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v 


SNfflBA 

BY 


I 


Silver  Print  on  Citro-Chloride  of  Silver  Paper.— Positive. 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/modernheliographOOIiet 


Ordinary  Blue  Print.— Negative. 


Ordinary  Blue  Print.— Positive. 


Direct  Cyanotype.   ( Pizzighellitype.) 


Ink  Picture. 


8 


Carbon  Print. 


9 


Uranium  Print,  Developed  with  Nitrate  of  Silver. 


Uranium  Print,  Developed  with  Red  Prusslate  of  Potash. 


MODERN 

HELIOGRAPHIC  PROCESSES : 

A 

MANUAL  OF  INSTRUCTION 

IN 

THE  ART  OF  REPRODUCING  DRAWINGS, 
ENGRAVINGS,  MANUSCRIPTS,  ETC., 

BY  THE 

ACTION  OF  LIGHT; 

FOR  THE  USE  OF 

ENGINEERS,  ARCHITECTS,  DRAUGHTSMEN,  ARTISTS 

AND  SCIENTISTS. 

« 

* 


ERNST  LIETZE, 

MECHANICAL  ENGINEER. 


D.  VAN  1STOSTEAND  COMPAISTY, 

NEW  YORK. 
1888. 


Entered,  according  to  Act  of  Congress,  in  the  year  1888,  by 
Ernst  Lietze, 

In  the  Office  of  the  Librarian  of  Congress,  at  Washington,  D.  C. 


presswork  by  john  wllson  and  son, 
University  Press. 


PllEFACE. 


The  present  book  had  its  origin  in  a  lecture  on  "  The  Heliographic 
Methods  of  Reproducing  Drawings,  Manuscripts,  Engravings,  etc."  read 
by  the  author,  November  17,  1885,  at  the  Ohio  Mechanics'  Institute. 
This  lecture  met  with  such  favor  and  applause  that  it  had  to  be 
repeated  January  9,  1886.  Thereupon  the  author  was  urgently  requested 
by  his  friends  to  publish  his  paper  in  the  form  of  a  pamphlet,  or  little 
book.  He,  at  length,  determined  to  do  this;  but  much  had  to  be 
added  —  many  recipes  tried  and  experiments  made  —  in  order  to  give 
the  work  the  value  which  the  author  wished  it  to  have.  He  who 
knows  how  often  an  experimenter  is  deceived  and  disappointed,  in  trying 
recipes  and  processes,  can  easily  imagine  why  the  publication  of  the 
book  was  so  long  delayed. 

An  abundance  of  excellent  and  valuable  works  on  photography 
already  exist,  but,  as  far  as  the  author  is  aware,  there  is  no  book,  in 
the  English  language,  which  is  adapted  to  the  special  use  of  the  Engi- 
neer, the  Architect,  and  the  Draughtsman,  who  may  wish  to  employ 
the  heavenly  light  as  a  copying  clerk.  All  that  has  been  written  and 
printed  for  this  purpose  is  scattered  through  the  numerous  scientific 
and  technical  periodicals. 

It  is  true  that  the  professional  photographer  and  the  photographing 
amateur  use  the  same  forces  of  nature  —  the  same  light  and  the  same 
chemicals — as  the  draughtsman  who  copies  his  drawings  by  a  helio- 
graphic process ;  but  it  is  also  true  that  the  heliographic  reproduction 
of  large  drawings,  etc.,  differs  as  much  from  photographic  printing  as 
does  the  work  of  a  carpenter  from  that  of  a  cabinet-maker,  or  the 
art  of  engine-building  from  that  of  watch-making. 

This  book  is  not  written  or  compiled  by  a  photographer,  nor  is  it 
intended  for  photographers;  but  it  is  gotten  up  by  an  engineer  and 
draughtsman,  for  the  use  of  his  professional  associates. 

Parts  of  the  following  pages  have  been  gathered  from  periodicals, 
portions  are  taken  from  standard  works  on  photography,  chemistry, 
and  physics,  and  a  great  deal  is  selected  and  translated  from  German 
works  on  the  subject. 

The  attentive  reader  will,  nevertheless,  observe  that  a  great  deal  of 
the  matter  is  original  with  the  author.  A  large  number  of  the  for- 
mulas given  have  been  tested  by  the  writer,  and  many  of  the  processes 
communicated  have  been  practiced  by  him  for  years.  Care  has  been 
taken  to  select  such  recipes  and  processes  as  may  be  useful  to  engi- 
neers, architects,  draughtsmen,  etc.  Formulae  which  are  of  no  value 
to  the  writer,  but  which  were  given  by  reliable  authorities,  and  which 
may  prove  useful  to  others,  are  also  added. 

iii 


~7%S5 


iv 


PREFACE. 


Some  of  the  processes  described  may  appear,  at  first,  to  be  imperfect, 
difficult  to  execute,  or  otherwise  open  to  objection,  but  they  may  be 
developed  and  usefully  applied  in  the  hands  of  intelligent  draughtsmen. 
In  order  to  support  this  statement,  the  history  of  the  "Blue  Print 
Process,"  which  is  now  so  universally  adopted,  needs  only  to  be  men- 
tioned. This  process  was  invented  by  Sir  John  Herschel,  in  1840 ;  but 
how  many  years  passed  before  it  was  esteemed  and  practically  intro- 
duced ! 

The  works  and  periodicals  from  which  the  writer  obtained  informa- 
tion, collated  recipes,  thoughts,  and  ideas,  which  were  tested,  compared, 
modified,  and,  together  with  his  own  experience,  compiled  into  the 
present  book,  are  the  following : 

Roscoe,  Henry  Enfield,  and  Schorlemmer,  Charles :  A  Treatise  on  Chemistry. 
Wood,  George  B.,  M.D.,  and  Bache,  Franklin,  M.D. :  The  Dispensatory  of  the 

United  States  of  America ;  Philadelphia,  1883,  J.  B.  Lippencott  &  Co. 
Fowler,  T.,  M.D. :  The  Silver  Sunbeam;  New  York,  E.  &  H. T.  Anthony  &  Co. 
United  States  of  America  Patent  Office  Reports. 
Abridgments  of  Specifications  of  English  Patents. 

Burton,  W.  K.,  C.E. :  The  A  B  C  of  Photography;  London,  1882,  Piper  &  Carter. 
Pettit,  Jas.  S. :  Modern  Reproductive  Graphic  Processes;  New  York,  1884,  D.  Van 

Nostrand. 
The  Scientific  American. 
The  Scientific  American  Supplement. 
The  American  Machinist. 

Heinlein,  H. :  Photographikon ;  Leipzig,  1864,  Otto  Spamer. 

Haugk,  Fritz :  Die  Modernen  Lichtpaus-Verfahren ;  Duesseldorf,  Ed.  Liesegang. 

Halleur,  D.  G.  C.  H. :  Die  Kunst  der  Photographie ;  Leipzig,  1853. 

Eder,  D.  J.  M. :  Die  Reactionen  der  Chromsaeure  und  der  Chromate  auf  Gelatine, 

Gummi,  etc. ;  Wien,  1878. 
Husnick,  J. :  Das  Gesammtgebiet  des  Lichtdrucks ;  Wien,  1880,  A.  Hartleben. 
Pizzighelli,  G. :  Anthrakotypie  und  Cyanotypie;  Wien,  1881. 
Pizzighelli,  J.  und  Huebl,  A. :  Die  Platinotypie. 

Vogel,  Dr.  H.  W. :  Die  Chemischen  Wirkungen  des  Lichtes ;  Leipzig. 

Talbot,  Romain:    Die  Benutzung  der  Photographie  zu  Wissenschaftlichen  und 

Technischen  Zwecken;  Berlin,  1883. 
Neueste  Erfindungen  und  Erfahrungen. 

The  patented  processes,  described  here,  are  inserted  only  to  give  a 
complete  view  of  the  subject  treated ;  as,  of  course,  they  can  not  be 
used,  except  by  permission  of  the  patentees. 

The  Specimens,  which  accompany  the  first  thousand  copies,  are  not 
at  all  intended  to  be  artistic,  but  merely  to  show  that  the  heliographic 
processes  may  be  employed  for  reproducing  any  kind  of  drawing,  print, 
or  manuscript.  The  originals  were  partly  tracings,  and  partly  woodcuts 
printed  on  tracing  paper. 

I  hope  the  contents  of  this  book  may  prove  as  useful  to  those  for 
whom  it  was  written,  as  they  have  been  to  me. 

Ernst  Lietze. 

Cincinnati,  O.,  1888. 


CONTENTS. 

Page. 


Preface   vii 

Introduction   1 

I.    Chemical  and  Physical  Action  of  Light   2 

II.    Classification  of  Heliographic  Processes   6 

III.  Paper   7 

IV.  Various  Methods  of  Sensitizing   8 

V.    Dishes  or  Trays  —  Devices  and  Machines  for  Sensitizing   10 

Glass  Dishes. 

Porcelain  Trays. 

Earthenware  Dishes. 

Trays  of  Hard  Rubber  or  Ebonite. 


Enameled  Sheet-iron  and  Cast-iron  Dishes. 
Japanned  Sheet-iron  Trays. 

A  Combination  Pan  for  Sensitizing  Large  Sheets. 
Temporary  Dishes  made  of  a  piece  of  Paper. 
Trays  made  of  Wood  or  Pasteboard  and  Lined 

with  India-rubber  Cloth. 
A  Device  for  Sensitizing  Large  Sheets  or  Small 

Rolls  of  Paper. 
Sensitizing  Machine  designed  by  Bertsch. 
Brush  for  Coating  Large  Sheets  by  Hand. 

VI.    Printing  Frames   16 

The  Cheapest  Miniature  Printing  Frame. 
A  Cheap  and  Convenient  Printing  Frame. 
Another  kind  of  Printing  Frame. 
The  Glass  for  Printing  Frames. 
The  Author's  Printing  Frame. 
The  Latest  Improvements  in  Printing  Frames. 
Pneumatic  Heliographic  Printing  Frame,  by  Hugo 
Sack. 

Prof.  Cleaves' s  Heliographic  Printing  Frame,  with- 
out a  Glass  Plate. 
V 


VI 


CONTENTS. 


VII.    How  to  Use  the  Printing  Frame 


Page. 
.  23 


VIII.    Exposure  to  the  Action  of  Light 


25 


IX.    Silver  Prints 


27 


1. 


Salts  of  Silver. 


Chloride  of  Silver. 
Iodide  of  Silver. 
Bromide  of  Silver. 
Nitrate  of  Silver. 


2.  Permanent  Sensitive  Chloride  of  Silver  Paper. 


Preparation  of  Paper  with  Arrow-root. 
Preparation  of  Paper  with  Gelatine. 
Preservation  of  Ordinary  Chloride  of  Silver  Paper. 


4.  How  Long  to  Expose  Silver  Prints. 

5.  Fixing  Silver  Prints. 

6.  "Washing  Fixed  Silver  Prints. 

7.  Toning  Silver  Prints. 

8.  Liesegang's  Combined  Toning  and  Fixing  Bath. 

9.  Silver  Prints  with  Development. 

10.  Talbot's  Calotype  Process. 

11.  Bromide  of  Silver  Emulsion  Process. 


Developing  and  Fixing  according  to  Eomain  Talbot. 
Eastman's  Directions  for  Developing  and  Fixing 

Prints  on  his  Permanent  Bromide  Paper. 
Preparation  of  the  Gelatine  Emulsion. 
Coating  Paper  with  the  Emulsion. 


1.  Sensibility  of  Ferric  Salts  —  Properties  of  Ferric  and  Ferrous 

Salts  —  Early  Discoveries. 

2.  Modern  Processes  by  which  Copies,  in  White  Lines  upon  a 

Blue  Ground,  are  Produced  from  a  Drawing  or  Tracing. 

Recipes  for  the  Sensitizing  Solution  for  Blue  Prints 


without  Development. 
Recipes  for  the  Sensitizing  Solution  for  Blue  Prints 

with  Development. 
Red  Prussiate  of  Potash  Prints. 
Toning  Blue  Prints. 

Silver  Negative  Blue  Positive  Prints.   (A  Patent.) 


Paper  prepared  with  Citric  Acid. 
Paper  prepared  with  Nitrate  of  Magnesia. 
Washed  Silver  Paper. 
Fuming  with  Ammonia. 


3. 


Ordinary  Chloride  of  Silver  Paper. 


X.    Processes  with  Salts  op  Iron 


51 


CONTENTS.  Vli 

Page. 

3.  Processes  by  means  of  which  Positive  Copies,  in  Blue  Lines 

upon  a  White  or  Light-colored  Ground,  are  Produced  from 
a  Drawing,  or  Tracing  (Direct  Positive  or  Cyanotypes). 
Pellett's  Process  (Patented). 

Pizzighelli's  and  Itterheim's  Positive  Cyanotype 
Process. 

Collache's  Direct  Blue  Print  Process. 

Joltrain's  Direct  Positive  Blue  Print  Process. 

A  Table  Comparing  the  Sensitizing  Solutions  for  the 

Direct  Positive  Blue-Print  Processes  according 

to  various  sources. 
Corrections  on  Blue  Prints. 

4.  Processes  by  means  of  which  Positive  Copies,  in  Dark- Violet 

Lines  upon  a  "White  or  Light-colored  Surface,  are  Produced 
from  a  Tracing  in  Black  Lines  (Ink  Pictures). 

Poitevin's  Process. 

Colas's  Formula. 

The  Author's  Modification. 

Fisch's  Method. 

5.  Poitevin's  Direct  Positive  Carbon  Prints. 

6.  Poitevin's  Process,  by  means  of  which  Positive  Copies  in 

Printing  Ink    are   Received  from  a  Tracing  in  Black 
Lines. 

7.  Dr.  Zoellner's  Iodide  of  Starch  Process. 

8.  The  Platinum  Process. 

William  Willis,  Jr.'s  Photo-Chemical  Printing. 
Pizzighelli's  and  Huebl's  Recipes. 
Captain   Pizzighelli's   New  Platinotype  Process 
Without  Development. 
XI.    Processes  with  Salts  op  Chromium   91 

1.  Processes  in  which  the  Reduced  Chromate  forms  the  Base 

of  the  Picture. 

Mungo  Ponton's  Chromium  Prints. 
M.  Guardabasiti's  Process. 

R.  B.  West's  Patents  on  Photographic  Printing. 

2.  Processes  in  which  the  Unaltered  Chromate  forms  the  Base 

of  the  Picture. 

Halleur's  Chromate  of  Silver  Prints. 

Cros  and  Vergerand's  Chromate  of  Silver  Process. 

Foxtype. 

Willis's  Aniline  Process. 

V.  J.  M.  Gottlieb's  Method  of  Reproducing  Draw- 
ings and  other  Line-Work  of  Art. 


Vlll 


CONTENTS. 


Page. 

3.  Processes  which  are  Based  upon  the  Property  of  a  Film  of 
Gelatine,  Gum,  or  the  like,  containing  a  Chromate,  to 
become  Insoluble  by  the  Action  of  Light. 
Poitevin's  Patent. 

M.  Tilhet's  Process  of  Reproducing  Drawings  and 


Designs. 

W.  W.  Sherman's  Process  of  Producing  Photo- 
graph's in  Permanent  Pigments. 
Ludwig  von  Itterheim's  Nigrographic  Process. 
Carbon  Prints,  according  to  Haugk  &  Liesegang. 
Carbon  Prints,  according  to  the  Author. 


4.  Processes  which  are  Based  upon  the  Property  of  Bichromated 

Gelatine,  Albumen,  etc.,  to  Receive  Fatty  Printing  Ink  in 
Places  upon  which  Light  was  allowed  to  Act,  while  the 
Parts  Untouched  by  Light  Imbibe  Water. 

Poitevin's  English  Patent. 

Captain  Abney's  Papyrography. 

5.  Dusting-In  Process. 

Mandel's  Patent. 


Anthracotypy. 


XII.    Processes  with  Salts  of  Uranium 


121  " 


XIII.  Two  Methods  for  Producing  the  Original  Tracing  as  a  Negative,  123 

XIV.  Table  of  Chemicals  mentioned  in  this  Book,  their  French  and 


German  Names,  Molecular  Weights,  Molecular  Formula, 
Composition,  Average  Price,  and  Remarks  Relating  to  their 


Principal  Properties  and  Preparation   125 


Index 


139 


MODEM  HELIOGrRAPHIC  PROCESSES. 


INTRODUCTION. 

Heliography,  or  Solar  Printing,  includes  all  those  processes  by 
means  of  which  drawings,  manuscripts,  copper-plate  and  other  engrav- 
ings, all  products  of  the  graphic  arts,  pattern  devices  and  designs,  such 
as  lace,  leaves  and  flowers  of  plants,  and  photographic  negatives  and 
positives,  which  allow  light  to  pass  through  them  unequally  in  different 
places,  may  be  reproduced  or  copied,  in  the  same  size  as  the  original, 
by  the  direct  action  of  light. 

When  the  number  of  copies  required  is  not  too  large,  the  Helio- 
graphic  or  Sunlight  Printing  Process  is  the  cheapest  method  of  repro- 
duction. For  large  editions,  however,  the  photo-mechanical  printing 
processes,  photo-lithography,  photo-zincography,  artotypy  (Lichtdruck), 
phototypy,  photo-engraving,  etc.,  as  also  the  purely  mechanical  means 
*of  anastatic  printing,  authography  and  zinc-etching  are  decidedly 
cheaper.*  These  last-named  processes,  however,  require  practical  knowl- 
edge and  experience  of  the  art,  and,  besides  these,  machinery  and  other 
costly  appliances,  while  Sunlight  Printing  can  be  performed  by  any 
one,  in  almost  any  room  or  office,  without  very  expensive  apparatus 
and  machines. 

Heliography  is  a  branch  of  the  photographic  art,  and  is  based 
upon  the  chemical  action  of  light  on  certain  bodies.  Heliography 
and  photography  are  similar  expressions.  The  former  signifies  sun- 
drawing  or  sun-writing,  and  the  latter  light-writing  or  light-draw- 
ing. Actinic  impressions  can  be  obtained  by  artificial  light,  by  the 
rays  emanating  from  other  fixed  stars  than  our  sun,  as  also  by  the 
electric  spark;  but  for  our  purpose  we  mainly  apply  light  that  comes 
directly  or  indirectly  from  the  sun. 

*The  Eastman  Dry  Plate  &  Film  Co.,  Rochester,  N.  Y.,  print  book  illustrations,  etc., 
on  Bromide  Paper  with  their  Photographic  Web  Printing  Press,  and  state  that  Bromide 
Prints,  in  editions  not  exceeding  two  or  three  thousand,  compete  in  price  with  those  made 
by  the  best  photo-mechanical  processes,  and  surpass  such  work  in  sharpness,  graduation 
of  tone  and  uniformity ;  being  made  from  the  original  negative,  nothing  is  lost  by  repro- 
duction. 


1 


I. 


CHEMICAL  AND  PHYSICAL  ACTION  OF  LIGHT. 

There  are  but  very  few  substances  which  are  not  affected  by  light. 
Almost  daily,  opportunities  present  themselves  for  observing  the  great 
influence  of  light  on  the  animal  and  vegetable  kingdoms ;  how,  at  times, 
it  produces  color,  and  how,  at  other  times,  it  bleaches  and  destroys 
color. 

It  would  seem  that  the  influence  of  light  on  organic  bodies  is  a 
phenomenon  which  must  have  attracted  the  attention  of  the  first  in- 
habitants of  the  earth.  Could  they  fail  to  mark  that  the  side  of  an 
apple  which  had  been  turned  toward  the  sun  was  of  a  beautiful,  bright 
red,  while  the  other  side,  which  had  not  received  the  direct  rays  of  the 
sun,  was  but  of  a  pale  green  or  yellow?  The  brilliant  and  rich  color- 
ation of  a  tropical  vegetation,  and  the  gradual  change  of  this  to  green, 
as  latitude  increases,  must  evidently  show  the  influence  of  light.  The 
changing  of  the  green  leaves  and  sprouts  of  plants  to  white,  when  sup- 
plied with  air  and  moisture,  but  not  with  light,  is  a  still  stronger  proof 
of  the  influence  of  light  on  vegetables. 

The  influence  of  light  upon  mankind  may  be  observed  in  the  bloom- 
ing cheeks  and  healthy  features  of  a  maiden  from  the  pastoral  lands  of 
the  sunny  Tyrolese  Alps,  as  contrasted  with  the  pale  and  colorless  facial 
expressions  of  miners,  who  are  always  in  the  dark,  or  with  the  inhabit- 
ants of  crowded  cities,  who  spend  the  greater  part  of  their  lives  in  dark 
homes  or  offices. 

Upon  inorganic  bodies  light  has  quite  a  similar  effect.  Sunlight  some- 
times combines  chemicals  to  form  one  compound,  and  at  other  times 
it  separates  a  compound  into  its  constituents.  Glass,  even,  is  affected 
by  light.  The  celebrated  physicist,  Faraday,  made  the  observation  that 
glass  colored  by  manganese,  and  conspicuous  for  a  peculiar  flesh  tint, 
rapidly  became  brown  in  the  light.  Prof.  Vogel  has  observed  and  re- 
corded a  very  interesting  example  of  this  kind.  A  handsome  plate 
of  glass  was  exhibited  in  a  mirror  store  in  Berlin.  It  bore  the  inscrip- 
tion, "  Manufacturer  of  Mirrors,"  in  brass  letters,  cemented  to  the  glass. 
After  having  been  exhibited  for  years,  the  business  failing,  the  plate  of 
glass,  on  account  of  its  beauty,  was  taken  away  by  the  proprietor.  The 
brass  letters  were  removed,  and  the  plate  was  cleaned.  To  the  surprise 
of  the  proprietor,  the  letters  remained  plainly  visible  on  the  glass,  not- 
withstanding all  attempts  made  to  remove  them.  The  surface  was 
abraded,  even,  but  this  did  not  produce  any  effect  on  the  letters.  It 
was  found  that  the  glass  was  traversed  by  yellow  marks,  and  that  it 
was  white  only  in  those  places  where  the  opaque  letters  had  kept  off 

2 


CHEMICAL  AND  PHYSICAL  ACTION  OF  LIGHT.  3 

the  light.  The  plate  of  glass  was  afterward  cut  into  two  pieces;  one, 
with  the  word  "  Mirrors,"  still  remains,  in  the  Philosophical  Collection 
of  the  University  of  Berlin. 

These  changes,  or  chemical  processes,  evidently  take  place  most 
rapidly  in  direct  sunlight;  less  so  in  diffused  light,  and  very  slowly — 
or  not  at  all — in  artificial  light.  The  latter  is  partly  due  to  the  insuf- 
ficient power  of  such  a  source  of  light,  and  partly  to  the  small  chem- 
ical action  of  certain  rays  of  light.  Thus,  the  effect  will  by  no  means 
be  the  same,  whether  bodies  are  exposed  to  yellow  or  to  blue  light. 
The  latter  acts  very  powerfully,  the  former  only  conditionally. 

In  order  that  we  may  represent  to  ourselves  a  perfect  picture  of  the 
chemical  and  physical  action  of  the  different  rays  of  light,  it  will  be 
necessary  for  us  to  dwell  a  little  on  the  decomposition  of  light. 

As  is  well  known,  a  ray,  or  a  pencil  of  rays,  of  solar  light  (or  white 
light  from  any  other  source)  can  be  decomposed  into  several  colored 
rays.  If  a  ray,  or  a  pencil  of  rays,  of  solar  light  be  admitted  into 
a  darkened  room,  through  a  small  aperture  (Fig.  1),  and  a  triangular 

prism  of  flint  glass  or 
quartz  be  placed  in  the 
path  of  the  pencil,  near 
the  aperture,  the  rays 
will  be  unequally  re- 
fracted, and  will  form, 
on  a  screen,  an  elon- 
gated colored  image, 
which  is  called  the  solar 
spectrum.  Newton  dis- 
tinguished seven  of  the 
colors  of  the  solar  spec- 
trum as  primary.  These 
are,  in  order,  beginning  with  the  least  refracted,  red,  orange,  yellow, 
green,  blue,  indigo  and  violet.  Newton  considered  all  the  prismatic 
colors  as  simple,  because  they  can  not  be  further  decomposed.  If  any 
colored  ray  of  the  spectrum  be  transmitted  through  a  small  aperture 
in  the  screen,  and  another  prism  be  placed  in  the  path  of  such  a  ray, 
it  will  again  be  refracted,  but  will  undergo  no  further  change  in  color. 

Physicists  now  consider  only  red,  yellow  and  blue  to  be  primary 
colors,  and  all  the  others  to  be  compounds.  Thus,  green  is  a  com- 
pound color ;  if  blue  and  yellow  rays  are  combined  by  means  of  convex 
lenses,  the  resulting  color  will  be  green.  If  certain  two  colored  rays 
are  collected — for  example,  if  green  and  red  rays  are  collected — colorless, 
or  white  light,  as  it  is  called,  will  be  produced.  Any  two  colors, 
which,  combined,  produce  white  light,  are  called  complementary  colors. 
Hence,  orange  and  blue,  violet  and  yellowish-green,  indigo  and  orange- 
yellow  are  complementary  colors. 


4 


MODERN  HELIOGRAPHIC  PROCESSES. 


Of  the  three  primary  colors  of  which  a  sunbeam  is  composed,  each 
is  a  representative  of  one  of  the  three  distinct  functions  of  light :  1st, 
to  illuminate;  2d,  to  heat,  and  3d,  to  produce  chemical  changes.  The 
illuminating  power  exists  mainly  in  the  yellow  rays;  the  heating  prop- 
erty in  the  red,  and  the  chemical  power  in  the  blue  rays.  Definitely 
speaking,  then,  it  is  not  light,  the  illuminating  agency,  which  is  the 
cause  of  photographic  action,  but  an  active  principle  associated  with 
it,  and  which  is  connected  chiefly  with  the  weakest  illuminating  and 
even  with  invisible  rays.  This  active  power  of  nature,  that  produces 
the  photographic  image  and  which  is  associated  with  light,  but  which 
is  not  the  illuminating  principle  called  light,  is  termed  actinism. 

Beside  the  seven  visible  rainbow  colors,  there  are  others — so-called 
invisible  rays — at  both  sides  of  the  visible  solar  spectrum  (Fig.  1). 
Those  beyond  the  red  make  known  their  presence  by  their  heating 
power;  those  beyond  the  violet,  by  their  chemical  action.  If  we  pass 
a  thermometer  over  the  solar  spectrum  slowly,  from  the  violet  to  the 
red,  we  will  notice  a  gradual  increase  in  temperature.  The  point  of 
maximum  intensity  varies  with  the  material  of  the  prism.  By  using 
a  prism  of  rock-salt,  which  absorbs  but  little  heat,  the  point  of  greatest 
heating  power  is  found  to  be  beyond  the  red  rays,  at  the  invisible 
ultra-red. 

The  relative  chemical  effect  of  the  different  rays  has  been  deter- 
mined by  placing  in  the  spectrum  a  slip  of  paper  covered  with  a  film 
of  a  substance  very  sensitive  to  actinism.  Quartz  prisms  have  been 
used  for  these  experiments,  as  they  are  better  adapted  to  this  purpose 
than  glass  ones,  because  glass  absorbs  a  large  portion  of  the  chemical 
rays.  The  chemical  effect  is  scarcely  perceptible  in  the  red  and  yellow 
rays ;  it  is  decidedly  apparent  in  the  blue,  and  attains  its  maximum  in 
the  violet.  The  action  extends  beyond  the  violet,  which  proves  that 
the  spectrum  contains  rays  more  refrangible  than  the  violet,  but  invis- 
ible. If  these  invisible  ultra-violet  rays  be  concentrated  by  a  quartz 
lens,  they  will  form  a  faint  beam  of  lavender  colored  light.  These 
rays  also  become  visible  when  they  fall  on  paper  moistened  by  a 
solution  of  quinine,  or  by  a  decoction  of  chestnut  shells,  or  if  they 
fall  on  glass  colored  by  the  uranium. 

Accordingly,  we  may  divide  the  rays  of  the  spectrum  into  three 
classes : 

1.  The  rays  of  heat :  Ultra-red,  red,  orange. 

2.  The  rays  of  light :  Orange,  yellow,  green. 

3.  The  actinic  rays :  Blue,  indigo,  violet  and  ultra-violet. 

Yellow,  which  offers  the  most  intensive  illuminating  power,  is,  chem- 
ically, nearly  inactive  on  most  of  those  substances  which  are  very  sens- 
itive to  sunlight. 

The  sources  of  artificial  light  radiate  mainly  yellow  rays,  and  this 
is  partly  the  reason  why  gas  and  lamp-light  have  but  little  influence 


CHEMICAL  AND  PHYSICAL  ACTION  OF  LIGHT. 


5 


upon  most  substances  which  are  sensitive  to  sunlight.  Bromide  of  silver, 
in  a  gelatine  emulsion,  the  most  sensitive  substance  known,  is,  neverthe- 
less, considerably  affected  by  yellow  gas  or  lamplight.  In  handling  this 
substance,  plates  or  paper  coated  with  it,  very  weak,  ruby-red  light, 
which  has  the  least  effect  upon  it,  must  be  used. 

The  property  of  quinine,  to  lower  the  tone  of  violet,  ultra-violet  and 
blue  rays — that  is,  to  convert  them  into  rays  of  less  refraction — is  used 
in  what  is  called  "The  Photography  of  the  Invisible."  If  a  writing  or 
chawing  is  made,  on  paper,  with  a  concentrated  solution  of  sulphate  of 
quinine,  the  result  will  scarcely  be  visible,  but  if  this  is  then  photo- 
graphed, it  will  appear  black  and  plainly  visible  in  the  picture. 

The  fact  that  colors  exist  which  we  can  not  see,  but  which  possess 
actinic  power,  and  that  certain  colored  rays  of  light,  which  possess  a 
great  illuminating  power,  produce  but  little  chemical  action,  is  one 
reason  why  photography  represents  many  objects  with  a  wrong  dis- 
tribution of  light  and  shade. 

The  intensity  of  moonlight  is  but  the  two-hundred-thousandth  part 
of  that  of  the  sun,  and  although  the  human  eye  can  easily  perceive 
objects  by  moonlight,  yet  a  photographic  plate,  exposed  to  a  lunar 
landscape,  will  scarcely  produce  a  picture  at  all.  The  photographic 
lunar  landscapes,  sometimes  offered  for  sale,  are  taken  by  daylight,  but 
very  darkly  copied,  so  as  to  resemble  the  effect  of  moonlight.  The 
comparatively  small  susceptibility  of  the  photographic  plate  to  feeble 
light  explains  the  reason  why  shadows,  in  photography,  are  generally 
too  dark. 


II. 


CLASSIFICATION  OF  HELIOGRAPHIC  PROCESSES. 

The  printing  processes  which  make  use  of  the  actinic  power  of  light 
are  very  numerous.  They  may  be  classified,  with  reference  to  the  sens- 
itive substances  used,  as  follows : 

1.  Processes  with  salts  of  silver.     3.  Processes  with  salts  of  chromium. 

2.  Processes  with  iron  salts.  4.  Processes  with  salts  of  uranium. 
The  processes  with  ferric  and  chromic  salts  may  be  divided  into 

direct  and  indirect  processes.  The  former  furnish  positives  from  posi- 
tives; the  latter,  negatives,  in  regard  to  light  and  shade,  from  positive 
originals.    All  processes  with  silver  and  uranium  salts  are  indirect. 

The  heliographic  processes  for  copying  drawings,  etc.,  in  which  silver 
salts  are  employed,  are  identical  with  the  photographic  processes  now 
universally  used.  The  photographer,  however,  generally  prints  from  a 
glass  negative,  while  the  draughtsman  reproduces  his  tracings  or  draw- 
ings. Silver  prints  are  somewhat  more  expensive  than  iron  prints;  but 
the  former  have  this  advantage  over  the  latter,  that  any  drawing  or 
print  may  be  copied  with  fair  results.  The  processes  with  ferric  and 
chromic  salts,  especially  those  by  which  dark  lines  are  produced  on  a 
white  or  very  light  surface,  require  originals  drawn  with  intense  black 
ink  on  very  thin  and  translucent  paper.  Silver  prints  of  small,  fine 
drawings  present  a  much  better  appearance  than  iron  prints.  One  of 
the  processes  with  iron  salts,  known  as  the  Herschel  Process,  and  which 
furnishes  the  so-called  "Blue-prints"  (white  lines  on  a  blue  ground),  is 
most  extensively  used  on  account  of  its  simplicity,  and  because  it  re- 
quires the  least  skill  and  experience.  It,  however,  has  the  disadvantage 
of  being  easily  destroyed,  as  all  alkalies  will  decompose  the  color. 
The  direct  processes,  with  iron  salts,  demand  more  practice  for  their 
execution  than  the  common  blue-print  process  or  the  processes  with 
silver  salts,  but  they  furnish  beautiful  prints.  Ink-pictures  are  as  durable 
as  pen-drawings  made  with  common  writing-ink.  Chromium  prints 
are  as  cheap  as  iron  prints,  and  some  of  the  processes  with  chromium 
salts  furnish  very  fine  reproductions  (e.  g.,  carbon  prints  and  nigrographic 
prints),  but  they  demand  some  skill  on  the  part  of  the  operator,  or  he 
will  be  successful  occasionally  only.  Such  iron  and  chromium  prints 
as  require  for  their  development  silver  or  platinum  salts,  cost  as  much, 
and  sometimes  more,  than  silver  prints.  Uranium  prints  are  easily 
made.  They  are  very  durable,  and  by  chemical  means  almost  inde- 
structible. They  will  even  withstand  the  action  of  a  boiling  solution  of 
cyanide  of  potassium. 

6 


III. 


PAPER. 

The  paper  used  for  heliographic  printing  should  have  a  smooth, 
hard  surface  and  a  fine,  uniform  texture.  There  are  in  the  market  cer- 
tain kinds  of  paper  specially  made  for  heliographic  purposes.  The 
materials  used  in  the  sizing  and  bleaching  of  the  paper  have  much  to 
do  with  its  qualification  for  this  purpose.  Several  manufacturers  of 
paper  advertise  chemically  pure  paper,  by  which  they  mean  that  no 
substances  have  been  used  in  sizing  and  bleaching  which  would  have 
any  undesirable  effect  on  the  chemicals  used  in  Sun  Printing. 

Several  kinds  of  writing  and  drawing-paper  may  also  be  used  for 
heliographic  copying.  One  kind  may  be  suitable  for  a  certain  process, 
another  kind  for  a  different  process. 

For  fine,  artistic  chloride  of  silver  prints,  it  is,  however,  preferable  to 
use  the  prepared  albumen  or  arrow-root  paper.  This  paper  is  coated 
With  a  thin  film  of  albumen  or  arrow-root,  which  film  closes  all  the 
pores,  thus  keeping  the  picture  on  the  surface.  Albumen  paper,  which 
can  be  obtained  in  any  photographers'  supply  store,  is  bright  and 
glossy,  and  the  most  brilliant  and  powerful  pictures  can  be  produced 
upon  it.  Photographers  use  it  almost  exclusively;  for  certain  special- 
ties they  must  use  plain  paper.  Arrow-root  paper  is  dull,  and  not 
as  much  used  as  albumen  paper.  The  prints  produced  upon  it  are 
hot  as  brilliant,  but  by  no  means  inferior  to  those  on  albumen  paper. 
Silver  prints,  on  plain,  uncoated  paper,  never  present  as  dark  or  power- 
ful a  picture  as  when  on  albumen  or  arrow-root  paper,  but  they  do 
Very  well  for  machine,  architectural  and  other  technical  drawings. 

For  iron,  chromium  and  uranium  prints,  many  different  kinds  of 
paper  are  suitable,  but  not  all.  It  is  always  best  to  try  a  small  sheet 
before  sensitizing  a  large  quantity  of  a  new  kind  of  paper. 


7 


IV. 


VARIOUS  METHODS  OF  SENSITIZING. 

In  order  to  render  paper  sensitive  to  the  action  of  light,  it  is  coated 
or  saturated  with  a  solution,  or  a  mixture,  of  certain  chemicals.  These 
chemicals  differ  according  to  the  process.  The  consistency  of  the  sensi- 
tizing substance  also  differs;  at  times  it  is  liquid,  like  water,  at  other 
times  stiff,  like  a  thick  solution  of  gum  arabic.  Two  or  more  operations 
are  sometimes  necessary  for  sensitizing  the  paper. 

Paper  may  be  sensitized  by  floating  it  upon  the  solution,  by  immers- 
ing it,  or  by  coating  it  with  the  sensitizing  substance  by  means  of  a 
brush,  sponge,  felt  or  india  rubber  roller,  by  hand  or  by  machine.  For 
solutions  which  are  liquid,  like  water,  a  sponge  or  a  soft  camel's-hair 
brush  is  the  most  suitable  appliance  when  sensitizing  by  hand.  If  the 
sensitizing  material  has  a  sirupy  or  still  stiffer  consistency,  a  hard  bristle 
brush  will  be  preferable.  Some  manufacturers  of  sensitized  paper  use  a 
machine  for  preparing  endless  or  roll-paper  for  certain  purposes.  We 
will  mention,  in  describing  the  various  processes,  which  method  of  sensi- 
tizing is  thought  to  be  the  best  in  each  special  case.  In  this  division 
we  intend  to  give  but  general  methods. 

If  the  paper  be  floated  upon,  or  immersed  in,  the  solution,  it  is  very 
important  that  the  paper  be  uniformly  moistened.  Air-bubbles  must  at 
once  be  removed. 

If  the  sensitive  material  is  to  be  applied  by  means  of  a  sponge  or 
brush,  pains  must  be  taken  to  coat  the  paper  as  uniformly  as  possible. 
It  is  well  to  go  over  the  paper  in  parallel  strokes,  taking  care  to 
leave  no  part  of  it  untouched,  using  plenty  of  the  solution  and  oper- 
ating so  quickly  that  no  part  will  be  dry  before  the  whole  is  coated. 
The  brush  or  sponge  should  then  be  pressed  out,  and,  nearly  dry,  ap- 
plied in  parallel  strokes,  in  a  direction  at  right  angles  to  the  first.  If 
the  sheet  be  so  large  that  one  person  can  not  go  over  it  with  sufficient 
rapidity  and  before  parts  of  it  become  dry,  two  men  must  be  engaged 
in  the  work,  and  commence  either  at  opposite  ends  or  in  the  middle  of 
the  sheet.  A  table  covered  with  oil-cloth  is  a  very  suitable  arrangement 
upon  which  to  place  the  paper  while  sensitizing  in  this  manner. 

In  most  cases,  floating  the  paper  will  distribute  the  liquid  more 
uniformly  than  any  other  method.  When  large  sheets  are  to  be  prepared, 
floating  becomes  impracticable  on  account  of  the  large  dishes  and  the 
large  quantity  of  sensitizing  solution  required  to  sufficiently  cover  the 
bottom  of  the  dish.  Moreover,  it  is  difficult  to  handle  large  sheets  for 
this  method. 

8 


VARIOUS  METHODS  OF  SENSITIZING. 


9 


The  best  way  to  prevent  air-bubbles  from  forming  under  the  paper, 
in  floating,  is  to  hold  it  at  two  diagonally  opposite  corners,  bend 
the  sheet,  and  then  allow  the  other  diagonal  of  the  sheet  to  touch  the 
liquid  first.  The  two  corners  held  in  the  hands  should  then  be  dropped, 
first  one  and  then  the  other.  This  may  sound  rather  elaborate  to 
some,  but  in  practice  it  is  very  simple,  and,  if  skillfully  executed, 
there  should  be  no  air-bubbles  formed.  Nevertheless,  it  is  always  best 
to  lift  the  paper  out  of  the  liquid,  after  a  short  time,  in  order  to  be  sure 
that  none  have  been  formed.  If  any  should  happen  to  have  been  formed, 
they  may  easily  be  broken  by  moving  the  paper,  while  half  of  it  is 
held  out  of  the  solution.  After  one  or  two  minutes,  the  paper  should 
be  removed  from  trie  bath,  by  drawing  its  surface  over  one  edge,  so  as 
to  drain  off  the  surplus  of  the  solution.  It  should  then,  if  the  sheet  is 
not  too  large,  be  hung  up  by  one  corner  to  dry.  Large  sheets,  how- 
ever, will  become  distorted  if  hung  up  by  one  corner;  they  must  be 
held  by  two  corners  or  by  three  or  more  places,  according  to  size,  along 
one  edge.  This  must  be  done  loosely;  that  is,  so  as  to  form  waves  in 
the  paper,  in  order  that  the  sheet,  while  drying,  may  contract  at  the 
upper  edge  just  as  in  other  parts.  A  thin,  but  wide,  strip  of  wood,  run- 
ning across  the  room,  and  supplied  with  spring  clothes-pins,  serves  very 
well  for  hanging  up  the  paper. 

When  the  author  wishes  to  sensitize  or  coat  paper  on  one  side  only, 
by  immersion,  he  pastes  two  sheets  together  by  their  edges,  or  folds  one 
sheet  in  the  middle,  and  trims  three  edges  of  one  half  a  little  smaller 
(about  £  inch)  than  the  other.  He  then  bends  the  three  edges  of  the 
larger  part  over  the  smaller  part,  and  pastes  the  edges  together.  As  a 
paste,  he  uses  shellac  varnish,  which  does  not  expand  the  paper  or  dis- 
solve in  the  solutions.  After  the  paper  has  been  immersed  and  dried, 
the  edges  which  were  pasted  together  by  the  varnish  are  trimmed  off. 


V. 


DISHES  OR  TRAYS,  DEVICES  AND  MACHINES  USED  FOR 

SENSITIZING. 

For  the  preparation  of  paper  by  floating  or  immersing,  as  also  for 
the  manipulations  of  fixing,  washing,  etc.,  flat  dishes  or  trays  are 
required.  They  must  be  water-proof,  and  the  material  of  which  they 
are  made,  or  the  protecting  covering  or  lining  of  the  same,  must  be  inert 
to  the  solutions  which  they  are  to  hold. 

Glass  Dishes  are  excellent,  but  the  largest  size  made  is  only 
16"X  20". 

Porcelain  Trays  can  be  had  as  large  as  19"X  24",  which  size  costs 
about  $12.00  apiece. 

Earthenware  Dishes  (called  Acid  dishes)  are  made  to  order,  up  to 
22"X  26",  and  cost  as  much  as  porcelain  dishes.  Glass  and  porcelain 
dishes  break  very  easily,  and  should  be  protected  by  wooden  frames. 

Trays  of  Hard  Rubber  or  Ebonite  have  the  advantage  of  not 
breaking  as  easily  as  those  of  glass  or  porcelain,  but  they  are  made  only 
of  sizes  as  photographers  require  them  for  the  development  of  dry  plates. 
The  largest  commercial  size  of  hard  rubber  trays  is  21"X  26"  (price, 
$8.75  to  $12.00,  according  to  depth) ;  larger  sizes  must  be  made  to  order 
in  an  india  rubber  factory. 

Enameled  Sheet  Iron  and  Cast  Iron  Dishes  are  very  durable,  but 
those  which  are  manufactured  are  not  of  sufficient  size.  They  must  be 
specially  made  for  the  purpose,  and  sent  to  the  enameling  works  to  be 
glazed.  Small  sizes,  up  to  19"X  24"  (price,  $15.00),  are  in  the  market 
under  the  name  of  "Agate  Ware  Pans." 

Japanned  Sheet  Iron  Trays  are  also  used  for  developing,  and  are 
a  great  deal  cheaper  than  those  just  named ;  the  largest  size  to  be  had 
is  20"X  24"  (price,  $2.50). 

A  Combination  Pan  for  sensitizing  large  sheets  of  paper  can  be 

made  of  a  strong  plate  of  glass  and  four 
strips  of  wood,  about  4  inches  wide  and  1 
inch  thick.  Fig.  2  represents  such  a  tray. 
Across  the  middle  of  one  of  the  sides  of 
each  of  the  four  strips  of  wood,  a  groove 
is  planed,  about  or  i"  deep,  and  as  wide 
as  the  glass  plate  is  thick.  The  grooves 
are  filled  with  putty,  and  the  glass  inserted. 
The  frame  is  then  screwed  together  with 
wood-screws.  Before  tightening  the  screws,  some  putty  should  be  placed 
at  the  joints,  and,  finally,  the  wood  should  be  varnished  with  shellac 

10 


DISHES  OR  TRAYS  USED  FOR  SENSITIZING. 


11 


Fig.  3. 


close  to  the  glass.  One  side  of  this  pan  can  be  used  for  sensitizing,  and 
the  other  for  washing,  silver  prints  after  having  been  taken  out  of  the 
copying  frame.  For  sheets  of  small 
size,  the  writer  uses — especially  while 
experimenting — Temporary  Dishes 
Made  of  a  Piece  of  Paper  by  bending 
or  folding,  as  shown  in  Fig.  3.  Accord- 
ing to  the  chemicals  to  be  used  in  them, 
the  paper  is  left  as  it  is,  varnished  with 
shellac,  or  saturated  with  parafine. 

Trays  Made  of  Wood  or  of  Pasteboard  and  Lined  with  India 
Rubber  Cloth  are  very  practicable,  light,  cheap  and  easily  made.  For 
immersing  large  sheets  of  plain,  salted  paper  in  the  silver  salt  solution, 
the  author  uses  a  light,  wooden  tray,  lined  temporarily  with  a  piece  of 
india  rubber  cloth,  which  is  bent  in  a  manner  similar  to  that  of  the 
paper  dish  illustrated  in  Fig.  3.  The  rubber  cloth  is  taken  sufficiently 
large  so  as  to  project  over  the  sides  of  the  tray  and  permit  bending  to 
the  outside,  where  it  is  fastened  by  means  of  thumb-tacks. 

Fig.  4  is  a  perspective  view,  and  Fig.  5  a  cross-section,  of  a  tray  of  a 
different  form,  for  drawing  sheets  of  paper  through  a  liquid.    This  tray 
has  the  advantage  over  others  of  requiring  but  a  small  amount  of 
liquid.    The  inside  is  to 
be  well  coated  with  a  suit- 
able varnish,  or  lined  with 
india  rubber  or  acid-proof 
cloth.    A  glass  tube,  T, 
closed  at  the  ends  by  in- 
dia rubber  stoppers,  or  by 
corks    impregnated  with 
parafine,  is  clamped  be- 
tween the  ends  of  the  box. 
In  Fig.  5,  Q  represents 

the  sheet  of  paper  to  be  sensitized.  At  the  corners  of  the  sheet,  loops 
of  threads  are  attached,  through  which  thin,  wooden  sticks  are  slipped, 
so  that  the  paper  can  be  held  by  the  sticks,  and  can  be  moved  back 
and  forth  to  the  extreme  ends,  in  the  liquid,  without  dipping  the  fingers 
therein. 

Figs.  6  and  7  illustrate  a  Device,  suggested  by  the  writer,  for  Sens- 
itizing Large  Sheets  or  Small  Rolls  of  Paper  by  Means  of  Rollers. 
Two  brackets,  as  A,  and  two  other  brackets,  as  B,  are  bolted  to  a  wall 
or  to  posts ;  the  first  pair  near  the  floor,  and  the  other  pair  near  the 
ceiling  of  the  room.  The  lower  brackets,  A,  are  provided  with  journal- 
boxes  for  the  iron  shaft  of  the  wooden  roller,  C,  to  rotate  in.  The 
upper  brackets,  B,  are  fitted  with  stems,  which  have,  at  their  upper 
ends,  forks,  in  which  the  iron  shaft  of  the  upper  wooden  roller,  E,  is 


Fig.  4. 


Fig.  5. 


12 


MODERN  HELIOGRAPHIC  PROCESSES. 


journaled.  The  paper  to  be  sensitized  or  coated  is  pasted  together 
(preferably  with  shellac  varnish)  to  form  an  endless  band,  and  is  placed 
over  the  rollers  C  and  E.  The  stems,  G,  are  pressed  upward  by  springs 
(invisible  in  the  sketch).  The  nuts,  H,  serve  to  adjust  the  distance 
between  the  rollers  C  and  E,  and  to  regulate  the  tension  of  the  paper 

band.  The  brackets,  B,  may  also  be  so 
arranged  that  they  can  be  made  to  slide 
up  and  down  on  the  wall  or  posts,  and 
fastened  at  any  desired  height.  Marks 
may  be  made  on  the  wall  or  posts  to 
indicate  the  position  which  the  brackets 
must  occupy  for  certain  lengths  of  paper. 
The  roller,  D,  is  covered  with  india  rub- 
ber, and  revolves  in  the  sensitizing  (or 
other)  liquid  contained  in  the  trough  or 
fountain,  F.  The  latter  (shown  in  the 
sketch  partly  in  section)  is  hinged  to 
the  brackets,  A,  and  provided  with  the 
eyebolts  and  nuts,  S,  for  bringing  the 
fountain  roller,  D,  in  contact  with  the 
paper  around  the  roller  C.  The  scrapers, 
N,  N,  reach  very  close  to  the  roller  D, 
and  prevent  a  too  large  amount  of 
solution  from  clinging  to  the  roller. 
The  caps  of  the  journal-boxes  of  the 
roller  C  are  so  arranged  that  they  can 
be  readily  opened  when  the  roller  is  to 
be  taken  out.  In  order  to  place  the 
Qp^3  paper,  which  has  been  previously  pasted 
together,  in  the  apparatus,  the  nuts  of 
eyebolts  S  are  first  turned  back  so  that 
the  fountain  F  hangs  down,  and  the 
roller  C  does  not  touch  the  fountain 
roller  D.  The  nuts  H  are  then  loosened 
so  that  the  stems  G  rise  up  by  virtue 
of  the  springs;  the  journal-boxes  of  the 
roller  C  are  opened,  and  the  rollers  C 
and  E  taken  out.  Then  the  paper  is 
placed  on  the  roller  E,  the  roller  put 
back  in  its  place,  the  roller  C  slipped 
in  the  endless  paper  band  and  let  down  easily,  so  that  the  paper  will  be 
tensioned  by  the  weight  of  roller  C.  Then  the  nuts  H  are  screwed  up 
until  both  journals  of  the  roller  C  just  touch  the  bottom  of  their  bear- 
ing-boxes; the  journal-boxes  are  closed,  and  the  paper  moved  in  such 
a  position  that  the  lap  of  the  same  is  directly  above  the  roller  D ;  then 


! 


Fig.  6. 


DEVICES  AND  MACHINES  USED  FOR  SENSITIZING. 


13 


the  nuts  of  bolts  S  are  turned  on,  until  the  roller  D  touches  the  roller 
C.  Finally,  the  hand-crank  L  is  put  on  the  projecting  end  of  roller  C, 
and,  by  means  of  it,  the  roller  C  is  turned — at  first  a  little  backward 
and  forward,  and  then  uniformly  in  one  direction — until  the  lap,  in 
the  paper  band,  again  comes  to  the  line  of  contact  of  the  two  rollers 
D  and  C.  While  turning  the  crank  backward  and  forward,  the  paper 
must  be  observed,  in  order  to  see  whether  the  solution  is  being  equally 
applied  at  either  side.  If  this  should  not  be  the  case,  one  or  the  other 
of  the  nuts  of  the  screws  S  must  be  tightened  or  loosened,  in  order  to 
cause  the  roller  D  to  press  uniformly  upon  the  roller  C,  and  with  as 
much  pressure  as  necessary  to  apply  the  required  amount  of  solution 
to  the  paper.  When  paper  of  various  widths  is  intended  to  be  coated 
in  this  apparatus,  it  is  best  to  arrange  the  lower  part  so  that  a  roller, 
O,  can  be  placed  between  the  rollers  D  and  C,  as  indicated  in  Fig.  7. 
The  length  of  the  rollers  O  and  C  should  correspond 
with  the  width  of  the  paper  to  be  coated,  while  D  and 
E  may  have  a  length  equal  to  the  width  of  the  widest 
paper. 

For  the  preparation  of  very  large  sheets  and  rolls 
of  paper,  for  certain  processes,  manufacturers  of  such 
paper  use  machines  to  do  this  work. 

By  means  of  a  machine,  paper  can  be  coated  more 
uniformly  than  is  possible  by  hand. 

In  the  following,  we  describe  and  illustrate  a  Sensi- 
tizing Machine,  designed  by  Bertsch  (according  to  Ed. 
Liesegang) : 

Fig.  8  is  a  side  elevation,  Fig.  9  a  front  elevation, 
and  Fig.  10  a  plan  or  top  view  of  the  entire  machine. 
Fig.  11  is  a  detail  view,  showing  the  arrangement  of  the  three  rollers, 
T,  R  and  U,  and  the  glass  scraper  X,  which  may  be  placed  between 
the  rollers  R  and  U,  so  as  to  press  against  the  paper  and  remove  a 
surplus  of  the  liquid.  The  principal  parts  of  this  machine  are  a  num- 
ber of  rollers,  P,  T,  R,  U,  S  and  V.  The  paper  to  be  prepared,  being 
rolled  up  on  the  roller  P,  is  carried  over  the  tension  segment  A,  and 
between  the  rollers  R  and  T.  The  latter  roller  is  covered  with  felt, 
and  revolves  in  the  fountain  F,  which  contains  the  sensitizing  liquid. 
The  inside  of  the  fountain  is  lined  with  gutta-percha. 

The  screws  B  serve  to  regulate  the  distance  between  the  rollers  T 
and  R.  The  paper,  after  passing  the  roller  R,  is  carried  over  the  roller 
U,  the  table  C,  and  the  roller  V.  An  endless  cloth,  stretched  over 
the  rollers  S  and  V,  and  moving  over  the  top  of  the  table  C,  carries 
the  paper  farther.  The  motion  of  the  endless  cloth  is  obtained  by 
the  rotation  of  the  roller  S,  which  is  driven  from  U.  The  wheels  H  H, 
over  which  rubber  rings  are  sprung,  press  upon  the  paper — still  wet  — 


14 


MODERN  HELIOGRAPHIC  PROCESSES. 


which  is  supported  by  the  endless  cloth,  and,  in  this  manner,  the  paper 
is  kept  under  tension  and  moved  forward. 

The  rollers  are  driven,  one  from  the  other,  by  means  of  gear-wheels, 
and  are  set  in  motion  by  the  fly-wheel  I,  which  is  fastened  to  the 
shaft  of  the  roller  U,  and  provided  with  a  handle  by  which  it  is 


Fig.  8.  Fig.  11.  Fig.  9. 


turned.  The  fountain  roller  T  is 
tjj  covered  with  felt,  and  applies  the 
sensitizing  solution  to  the  paper. 
The  paper,  leaving  the  endless  cloth, 
passes  over  a  number  of  rollers  (not 
shown  in  the  figures),  and  is  finally 
dried  upon  laths. 

The  ratio  of  the  gearing  is  so 
selected,  that  T  moves  considerably 
faster  than  R,  and  opposite  to  the 
same. 

Before  the  machine  is  set  in  mo- 
tion, the  roller  T  is  withdrawn  from 
the  roller  R,  by  means  of  the  screws 
B,  and  swiftly  turned,  in  order  to  wet  its  felt  covering  uniformly. 
After  this  has  been  done,  the  paper  is  guided  over  the  tension  segment 
A,  and  the  roller  R;  then  the  roller  T  is  brought  in  contact  with  the 
paper  on  roller  R,  the  fly  slowly  turned,  and  the  paper  guided  over 
the  roller  U,  and  under  the  wheels  H.  Then  the  machine  is  set  in 
regular  motion,  so  that  the  fly-wheel  will  make  from  30  to  40  revolu- 
tions per  minute. 

Every  time,  after  using  the  machine,  the  sensitizing  solution  remain- 
ing must  be  removed,  and  the  fountain  and  the  rollers  cleaned  by 
washing  them  with  plenty  of  water. 


Fig.  10. 


DEVICES  AND  MACHINES  USED  FOR  SENSITIZING. 


15 


In  Fig.  12,  we  illustrate  A  Brush,  recommended  by  a  friend  of  the 
writer,  for  Coating  Large  Sheets  by  Hand.  This  brush  consists  of 
two  thin  boards,  of  suitable  form,  well  var- 
nished with  shellac,  between  which  a  number 
of  thicknesses  of  cotton  or  woolen  flannel  are 
placed,  so  as  fo  project  at  one  side,  and  which 
are  then  fastened  together  by  means  of  wood- 
screws.  The  brush  may  be  made  as  wide  as 
the  width  of  the  paper,  and  a  trough,  as  that 
shown  in  Figs.  4  and  5,  of  corresponding  length,  may  be  used  for  the 
solution. 


VI. 


PRINTING  FRAMES. 

The  printing  or  copying  process  is  very  simple,  and,  with  a  little 
attention,  may  be  learned  in  a  short  time.  A  copying  frame,  of  suit- 
able size,  is  the  only  apparatus  required.  This  apparatus  has  been 
made  in  various  ways,  but  all  have  the  same  object  in  view,  namely, 
to  hold  the  paper  in  close  contact  with  the  tracing,  drawing,  negative, 
or  other  original. 

The  Cheapest  Miniature  Printing  Frame  is  the  toy  known  as  the 

"  Transparent  Drawing 
Slate,"  and  may  be  used, 
by  beginners,  to  prac- 
tice with.  The  ground 
glass  plate,  in  this  frame, 
will  necessitate  a  some- 
what longer  exposure,  for 
copying,  than  a  clear, 
transparent  plate  would. 

A  Cheap  and  Con- 
venient Printing  Frame 
of  small  size,  similar  in 
construction  to  a  transparent  drawing-slate,  but  more  substantially  made, 
is  illustrated  in  Figs.  13  and  14. 

Another  Kind  op  Printing  Frame  is  shown  in  Figs.  15,  16  and 
17.    This  frame  is  so  constructed,  that  the  original  drawing  or  negative 


Figs.  13  and  14. 


Fig.  15. 


to  be  copied,  or  the  sensitized  paper,  may  be  longer  than  the  frame 
and  project  over  the  ends  of  it.  The  projecting  part  of  the  paper  may 
be  rolled  up,  wrapped  and  protected  from  the  action  of  light.  This 

16 


PRINTING  FRAMES. 


17 


arrangement  enables  the  operator  to  copy  different  small  drawings,  or 
parts  of  large  drawings,  one  after  the  other,  on  one  sheet  of  paper. 


Figs.  18  and  19  represent  a  type  of  printing  frame  frequently  met 
with. 

The  Glass  for  a  Printing  Frame  should  be  plate  glass,  with  a  per- 
fectly even  surface,  and  of  sufficient  thickness 
(  i"  to  -J")  to  withstand  the  pressure. 

For  copying  very  large  drawings,  the  author 
has  constructed  a  'printing  frame,  which  is  illus- 
trated in  Figs.  20  to  24. 

Fig.  20  is  a  longitudinal  section,  and  Fig. 
21  a  transverse  section,  of  the  whole  apparatus. 

Figs.  22  to  24  are  detail 
views.  Fig.  22  shows  the 
ratchet-wheel  and  pawl 
of  the  eccentric  shaft; 
Fig.  23  a  portion  of  the 
framed  glass,  and  Fig. 
24  a  part  of  an  axle,  with 
a  wheel.  The  scale  of 
is  1\  inches  to  a  foot. 


Fig.  18. 


21 


The  apparatus  consists  of 


Fig.  20  is  -J  inch  to  a  foot,  that  of  Fig 
Figs.  22  to  24  are  drawn  in  £  of  full  size, 
a  board,  mounted  on  wheels,  and  resembling  a  platform-car;  a  stand, 
provided  with  rails  for 
the  former  to  run  upon, 
and   a  plate   of  glass 
held  in  a  frame.  The 
board  is  covered  with  a 
blanket  of  felt,  billiard- 
cloth,  or  the  like. 

The  stand,  with  the  FlG  19 

rails,  is  placed  close  to 

a  window.  The  rails  extend  out  of  the  building,  and  are  trussed  to  the 
wall.    The  stand  is  somewhat  longer  than  twice  the  length  of  the  board. 


PRINTING  FRAMES. 


19 


At  the  sides  of  the  stand,  long,  wooden  lifters  are  arranged,  for  elevating 
and  lowering  the  glass  plate.  These  lifters  are  pivoted  to  brackets,  at 
the  end  of  the  stand,  opposite  the  window,  and  rest,  near  the  win- 
dow, upon  eccentrics.  The  latter  are  fastened  to  a  shaft,  which  is 
journaled  in  the  stand.  This  shaft  is  also  provided  with  a  hand- 
wheel,  by  which  it  can  be  turned,  and  with  a  ratchet-wheel,  which 
allows  the  shaft  to  be  turned  only  in  one  direction,  except  when  the 
pawl  is  released.  The  glass  plate  is  bounded,  on  three  sides,  by  a 
wooden  frame,  and  on  the  fourth  side  by  a  small  iron  or  steel  bolt, 
joining  the  longitudinal  sides  of  the  frame  at  their  inner  ends.  By 
means  of  the  eccentric  shaft,  the  lifters,  and  with  them  the  glass  plate, 
can  be  raised  and  lowered.  When  elevated,  the  glass  plate  rests  upon 
the  lifters,  and  the  board  may  be  rolled  back  alone.  In  order  to  place 
the  copying  paper  and  the  original  upon  the  platform,  this  and  the 
lifted  glass  plate  must  occupy  the  positions  in  which  they  are  drawn 
in  full  lines  in  the  longitudinal  Section,  Fig.  20.  The  light  must  be 
subdued  by  a  curtain  (of  an  inactinic  color),  which  is  attached  to  the 
window.  If  there  are  other  windows  in  the  room,  near  the  printing 
frame,  they  should  also  be  provided  with  curtains  for  this  purpose.  A 
number  of  smooth  sheets  of  paper,  which  are,  together,  a  little  thicker 
than  the  head  of  a  thumb-tack,  are  to  be  placed  under  the  sensitized 
paper.  The  original,  projecting,  toward  the  window,  a  little  over  these 
sheets,  is  fastened,  by  means  of  thumb-tacks,  to  the  board.  When  this 
has  been  done,  the  platform  is  rolled,  a  short  distance,  under  the  elevated 
glass  plate;  then  the  glass  is  let  down,  by  turning  the  eccentric  shaft 
slowly,  until  its  inner  end  rests  and  presses  upon  the  paper  on  the 
board,  the  other  end  of  the  glass  plate,  near  the  window,  still  remaining 
supported  by  the  side  arms,  but  only  slightly  elevated.  (We  should 
here  mention  that  the  inner  lower  edge  of  the  glass  must  be  made 
smooth  by  means  of  a  triangular  saw- file.)  The  platform-car  is  then 
rolled  farther  under  the  glass,  whereby  the  projecting  ends,  of  the  longi- 
tudinal sides  of  the  frame  of  the  glass  plate,  will  touch  the  window- 
sash.  The  rounded  corner  of  the  glass  tends  to  smoothen  the  paper  on 
the  board.  This  action  should  be  assisted  by  rubbing^  with  the  hands, 
crosswise  over  the  original,  and  starting  from  the  center,  while  sliding 
it  under  the  glass.  Before  the  original  is  entirely  under  the  glass,  the 
ratchet-wheel  is  released  from  its  pawl  and  the  eccentric  shaft  turned, 
so  that  the  whole  glass  plate  will  rest  upon  the  board  and  clear  the 
lifters.  Then  the  board  is  pushed  entirely  under  the  glass,  the  curtain 
raised,  the  window  opened,  and  the  platform,  loaded  with  the  glass  plate, 
rolled  out  into  the  sunshine.  This  position  is  indicated,  in  Fig.  20,  by 
dotted  lines.  If  tacking  the  original  to  the  board  should  be  objection- 
able, the  platform,  with  the  papers,  may  be  rolled  at  once  entirely  under 
the  elevated  glass  plate,  which  is  then  let  down  upon  it.  After  the 
exposure  to  the  action  of  the  light,  the  frame  is  rolled  in,  the  window 


20 


MODERN  HELIOGRAPHIC  PROCESSES. 


closed,  the  curtain  dropped,  the  glass  plate  elevated,  and  the  print  taken 
out  and  preserved  in  the  dark  for  the  next  treatment. 

The  Latest  Improvements  in  Printing  Frames  are:  (1)  The  ap- 
plication of  air-cushions,  in  place  of  the  felt  or  cloth  blankets,  to  insure 
a  perfect  contact  of  the  sensitized  paper  and  the  original. 

(2)  An  apparatus  for  producing  a  partial  vacuum  between  an  india 
rubber  blanket  and  the  glass  plate,  so  as  to  cause  the  exterior  atmos- 
pheric air  to  press  the  blanket,  the  sensitized  paper,  and  the  drawing 
or  original,  firmly  against  the  glass. 

(3)  Printing  frames,  with  curved  surfaces  and  without  a  glass  plate 
(especially  adapted  for  large  prints). 

The  Air-Cushion  is  generally  made  of  two  sheets  of  vulcanized 
india  rubber,  of  the  same  size,  which  are  connected,  air-tight,  by  their 
edges.  In  some  cases  it  consists  of  one  sheet  of  india  rubber,  fastened 
to  the  edges  of  a  thin  and  flexible  plate  of  zinc,  tin,  iron,  or  the  like. 
The  cushion  is  filled  with  air,  either*  by  blowing  into  it  with  the  mouth 
through  a  suitable  pipe,  or  by  means  of  bellows,  or  with  an  air-pump 
consisting  of  an  india  rubber  ball,  terminating  in  a  hose  and  provided 
with  suitable  valves,  which  is  operated  by  alternately  compressing  the 
ball  and  releasing  it  from  the  pressure. 

A  printing  frame,  provided  with  an  air-cushion,  has  been  patented 
by  Street  (United  States  patent  No.  263,242). 

An  advantage  of  the  vacuum  printing  frame  is,  that  the  glass  plate 
will  not  be  strained,  since  the  atmosphere  presses  equally  on  both  sides 
of  the  glass,  and,  therefore,  thinner  glass  plates  may  be  used. 

In  Figs.  25  to  32,  we  illustrate  the  Pneumatic  Heliographic  Print- 
ing Frame,  by  Hugo  Sack  (United  States  patent  No.  324,960).  The 
frame  K  holds  the  glass  plate  A,  which  is  of  common  white  ;window 
glass,  but  without  flaws.    The  original,  B,  to  be  copied,  and  the  sensi- 


Figs.  25,  26,  27  and  28. 


PRINTING  FRAMES  H.  SACK'S  PNEUMATIC. 


21 


tized  paper,  C,  are  placed  upon  the  glass.  The  rubber  cover  F  has  two 
beads  extending  around  one  side,  near  the  edges,  and  is  fastened  to  a 
second  frame.  This  second  frame  fits  loosely  into  the  opening  of  the 
main  frame  K,  to  which  it  is  hinged,  and  can  be  pressed  lightly  against 
the  glass  plate  by  means  of  the  swivels  L,  whereby  the  projecting  beads 
will  effect  an  air-tight  joint  between  the  glass  A  and  the  rubber  F. 
Inside  of  the  beads,  a  woolen  fabric,  E,  which  allows  the  air  to  escape 
through  its  porous  mass,  is  , 
pasted  to  the  rubber  cover. 
Between  this  and  the  sensi- 
tized paper  C,  a  strong 
pressed-board  or  cardboard, 
or  a  thin  pasteboard,  D,  is 
put,  to  prevent  the  wrinkles, 
etc.,  which  may  be  in  the 
original  drawing,  from 
affecting  the  porous 
woolen  cloth. 

The  hose  H  con- 


nects the  space,  be- 


Figs.  29  and  32. 

tween  the  rubber  cover  F  and  the  glass  plate,  with  an  air-pump,  which 
is  shown  in  detail  in  Figs.  30  and  31,  and  which  is  fastened  to  the 
frame  K,  and  also  serves  as  a  handle  for  the  frame.   (See  Figs.  25  and  29.) 

After  the  air  in  the  frame  has  been  rarefied  by  means  of  the  pump, 
the  external  atmospheric  pressure,  acting  equally  upon  the  glass  plate 
and  the  rubber  cover,  will  press  the  sensitized  paper  forcibly  against  the 

drawing.  The  frame  is  now 
ready  for  exposure  to  light. 
By  turning  back  the  nut  N 
of  the  hose-coupling  (Fig. 
30),  the  air  will  be  allowed 
to  enter  the  suction-pipe, 
and  the  vacuum  will  be  re- 
lieved. 

Fig.  25  illustrates  an  ap- 
paratus of  this  kind,  of  large 
size,  in  elevation.  In  small  sizes,  the  cross-pieces  q  q,  in  the  frame  of 
the  rubber  cover,  are  not  necessary.  The  printing  frame  is  conveniently 
supported  by  a  rolling  stand,  shown  in  Figs.  25  to  28.  It  will  be 
noticed  that  this  stand  rests  upon  three  points ;  namely,  on  two  wheels 
and  one  leg,  and,  therefore,  will  stand  firmly  everywhere,  even  on  a  floor 
which  is  not  perfectly  smooth.  The  two  wheels  are  attached  to  separate 
axles,  which  can  be  moved  in  and  out,  and  fastened  to  the  frame,  by 
means  of  set-screws.  In  this  manner  the  gauge  of  the  wheels  W  W  may 
be  changed.    When  adjusted  to  the  smallest  gauge,  the  frame  can  con- 


Fiq.  31. 


Fig.  30. 


22 


MODERN  HELIOGRAPHIC  PROCESSES. 


veniently  pass  through  narrow  doors,  and,  with  extended  axles,  it  can 
not  easily  be  upset  by  the  wind. 

Prof.  Cleaves'  Heliographio  Printing  Frame  Without  a  Glass 
Plate  merely  consists  of  a  cylinder,  having  a  length  exceeding  that  of 
the  widest  drawing  to  be  reproduced,  and  a  diameter  such  that  the 
longest  tracing  to  be  used  can  be  wrapped  around  it  and  still  leave  sufficient 
space  for  the  clamps  by  which  it  is  drawn  and  held  into  place. 

The  cylinder  is  smoothly  covered  with  felt,  and  the  sensitive  paper 
carefully  wrapped  about  it.  The  tracing  to  be  copied  is  drawn  over 
the  whole,  and  held  smoothly  in  place,  by  spring  clamps,  which  seize 
its  ends. 

It  is  found  easy  to  lay  the  tracing  smoothly  over  the  surface  and 
to  draw  it  into  contact,  and  that  the  work  done  by  this  method  is  even 
better  and  more  certain  than  that  produced  by  the  ordinary  plate-glass 
apparatus,  even  with  the  air-cushion  now  so  successfully  used  with  it. 

It  is  easy,  with  a  little  care  and  with  some  practice,  to  make  these 
prints  absolutely  perfect — much  easier  than  with  glass. 

The  apparatus  being  ready  for  use,  it  is  mounted  on  a  cradle,  sup- 
ported by  its  gudgeons,  and  is  revolved  in  the  sunlight  by  means  of  a 
cord,  leading  from  some  convenient  line  of  shafting ;  or  it  may  be  turned 
by  hand,  until  the  exposure  is  satisfactorily  completed.  It  requires  a 
little  more  time  to  print  a  sheet  by  this  method  than  by  the  old,  as 
the  tracing  and  the  underlying  sensitive  paper  are  exposed  but  one  half 
at  a  time  to  the  rays  of  the  sun.  With  exceptionally  large  prints, 
however,  for  which  only  this  process  would  be  employed,  this  is  not 
an  important  matter.  They  are  not  likely  to  be  made  every  day. 
(Extract  from  memoranda  presented  by  Prof.  R.  H.  Thurston,  at  Washington 
Meeting  of  Mechanical  Engineers,  1887.) 


VII. 


HOW  TO  USE  THE  PRINTING  FRAME. 

The  main  requirement,  for  obtaining  definite  and  clear  copies,  is  to 
bring  the  original  in  perfect  contact  with  the  sensitized  paper.  This  is 
easily  effected  with  small  sheets  of  paper.  The  pressure  of  the  springs 
or  screws  of  the  printing  frame,  or  the  weight  of  the  glass  plate  and  a 
single  blanket  of  flannel,  or  a  number  of  sheets  of  paper,  is  sufficient 
for  this  purpose.  Large  sheets  of  paper,  which  are  often  kinky,  some- 
times render  it  difficult  to  place  them  smoothly  into  the  ordinary 
plate-glass  apparatus.  In  such  cases,  thick  blankets  of  flannel,  or 
woolen  cloth,  or  an  air-cushion,  may  be  used  to  advantage.  An 
excellent  method,  recommended  by  Prof.  Vogel,  when  many  copies  are 
to  be  made  from  the  same  drawing,  is  to  stretch  the  original  upon  the 
glass  plate,  just  as  draughtsmen  stretch  their  paper  upon  the  drawing- 
board.  This  is  done  by  bending  over  about  ^  inch  of  the  sheet  around 
the  edges,  dampening  the  back  of  the  paper,  except  the  margin  bent 
over,  by  means  of  a  wet  sponge,  applying  mucilage  to  the  margin  and 
fastening  the  paper  to  the  glass.  The  writer  sometimes  stretches  the 
original  (a  tracing,  drawing,  engraving,  or  paper  negative)  over  a  frame, 
and  places  it,  with  the  sensitive  paper  underneath,  between  two  glass 
plates,  the  lower  of  which  is  a  little  smaller  than  the  inside  of  the 
frame.  With  an  ordinary  glass  plate  frame,  we  proceed  as  follows : 
The  frame  is  opened,  and  the  drawing,  tracing,  or  other  orignal,  is 
placed  upon  the  glass  plate,  which  has  been  previously  cleaned.  The 
sensitive  paper  is  placed  upon  the  original,  and  after  this  has  been 
smoothened  and  brought  into  the  correct  position,  the  blanket,  or  a 
number  of  sheets  of  blotting  or  other  soft  paper,  is  placed  on  top 
of  this.  The  frame  is  then  closed  and  examined  from  the  outside,  to 
see  whether  the  original  is  smooth,  shows  no  wrinkles  and  touches  the 
glass  uniformly.  If  this  should  not  be  the  case,  or  if  the  sensitive 
paper  should  not  be  in  the  right  position,  the  frame  must  again  be 
opened,  or  partly  opened,  and,  by  means  of  drawing  and  rubbing  the 
papers  and  the  blanket,  and  by  inserting  pieces  of  soft  paper,  the  whole 
must  be  made  perfectly  smooth. 

The  sensitized  paper  is  placed,  in  all  kinds  of  frames,  with  the  pre- 
pared side  touching  the  original,  except  in  cases  where  very  thick 
originals  are  to  be  copied,  and  where  the  sensitive  paper  is  very  thin. 
In  such  cases,  positive  prints,  in  regard  to  position,  may  be  obtained 
from  positives  by  putting  the  back  of  the  sensitive  paper  upon  the 
face  of  the  original. 

23 


24 


MODERN  HELIOGRAPHIC  PROCESSES. 


Care  must  be  taken  that  the  prepared  paper  be  dry  before  it  is  put 
into  the  printing  frame,  otherwise  the  original  would  be  stained,  wrinkled 
and  spoiled,  and  this  would  cause  the  prints  also  to  be  defective  and 
indistinct. 

It  is  evident  that  the  sensitized  paper  must  be  handled  and  placed 
into  the  frame  in  weak  light. 

The  original  drawing  or  tracing,  or  the  negative,  must  be  placed  into 
the  frame  in  one  of  the  following  positions : 

(1)  If  the  positive  tracing,  drawing,  or  engraving  to  be  copied,  is 
made  on  very  thin  paper  or  tracing  cloth,  and  if  a  print  positive  in 
regard  to  position  is  wanted,  the  face,  or  picture  side,  of  the  original 
must  come  in  contact  with  the  glass. 

(2)  If  a  negative  is  to  be  copied,  and  a  positive  copy  is  wanted,  or 
if  a  negative  print  is  to  be  made  from  a  positive  original,  the  back  of 
the  original  must  touch  the  glass.  Also,  when  the  original  positive 
drawing,  writing  or  engraving  is  made  on  thick  paper,  the  back  of  the 
same  must  be  in  contact  with  the  glass  (for,  if  the  opaque  lines 
of  an  original,  on  thick  paper,  were  to  touch  the  glass  plate,  the 
resulting  print  would  not  be  distinct,  as  the  light  would  spread  in  the 
paper  under  the  opaque  lines).  To  be  sure,  the  print  will  be  negative, 
in  regard  to  position;  but,  if  this  is  objectionable,  a  positive  can  be 
made  from  it. 


VIII. 


EXPOSURE  TO  THE  ACTION  OF  LIGHT. 

In  regard  to  the  time  of  exposure  to  light  required  in  each  special 
process,  to  obtain  a  useful  print,  a  definite  number  of  minutes  and 
seconds  can  not  be  given.  This  time  depends  as  much  upon  the  in- 
tensity of  the  light,  and  upon  the  thickness  and  the  degree  of  trans- 
parency of  the  paper  of  the  original,  as  upon  the  sensitiveness  to  light 
of  the  chemicals  used  in  the  process. 

It  is  evident  that  at  about  noon,  when  the  sunlight  is  the  most 
powerful,  the  printing  process  will  go  on  a  great  deal  faster  than  in 
the  morning  or  afternoon,  when  the  light  possesses  a  smaller  amount 
of  actinic  power.  It  is  also  evident  that  it  requires  a  longer  time  for 
light  to  pass  through  thick  paper  than  through  thin  or  very  translucent 
paper,  and  that  from  very  thick  drawings  no  prints  will  result. 

The  author  has,  however,  succeeded  in  taking  excellent  blue  prints 
from  patent  drawings  which  were  made  on  Reynolds'  bristol-board 
(three  sheets  thick),  by  first  making  a  negative  on  thin  Helios  paper, 
and  then,  from  this,  as  many  positives  as  were  wanted.  The  exposure 
for  the  negative  blue  print  required  3  days,  in  the  best  sunlight  in  June. 
The  positives  were  copied  in  from  40  to  45  minutes.  The  exposure  for 
a  negative,  on  bromide  of  silver  paper,  through  a  similar  original  draw- 
ing, would  require  less  than  one  minute  in  the  light  from  a  student- 
lamp. 

Furthermore,  the  color  of  the  paper  of  the  original  comes  into  con- 
sideration. Drawings  on  yellowish  paper  require  more  time  for  copying 
than  those  on  perfectly  white  paper;  and  drawings  or  engravings  on 
paper  of  a  certain  yellow  color  that  excludes  almost  all  actinic  rays  of 
light  can  not  be  copied  at  all. 

Much  of  the  success  in  sunlight  printing  depends  upon  the  ink  used 
in  the  execution  of  the  original.  If  the  lines  of  the  original  are  per- 
fectly black  and  opaque,  the  copies  will  be  good  and  well  defined,  and 
an  over-exposure  will  do  no  harm;  but  if  pale  ink  was  used  in  the 
original,  the  prints  will  be  poor.  When  drawings  or  engravings  exe- 
cuted with  pale  ink  are  to  be  copied,  it  is  recommended,  by  some 
authorities,  to  print  in  the  shade,  or  to  weaken  the  light  by  stretching  a 
sheet  of  thin  white  or  light-blue  paper  over  the  printing  frame. 

As  it  is  almost  impossible  to  determine  beforehand  how  long  the 
exposure  must  be  continued,  the  printing  frame  must  be  taken,  from 
time  to  time,  into  weak  light,  in  order  to  ascertain  how  far  the  process 
has  advanced.    For  this  purpose,  printing  frames  are  so  constructed, 

25 


26 


MODERN  HELIOGRAPHIC  PROCESSES. 


that  a  part  may  be  opened  and  the  print  examined,  while,  in  the  other 
part,  the  print  and  the  original  are  kept  in  contact  and  prevented  from 
slipping.  With  a  large  frame  this  operation  is  very  troublesome,  and, 
in  certain  processes,  we  can  not  judge  from  the  color  of  the  print  whether 
it  has  been  exposed  sufficiently  long.  For  this  reason  it  is  advisable 
to  use  a  small  glass  plate,  under  which  are  exposed  small  strips  of  the 
same  paper,  below  a  small  drawing  made  on  the  same  material  as  the 
original.  From  time  to  time  one  of  these  strips  may  be  pulled  out  and 
treated  as  the  process  requires,  and  the  progress  of  the  main  print  thus 
ascertained.  In  some  quick-acting  processes,  it  becomes  necessary  to 
cover  the  printing  frame  and  the  small  glass  plate,  or  to  take  them 
in  the  dark  or  in  weak  light,  during  the  time  that  the  specimen  is 
being  tested. 


IX. 


SILVER  PRINTS. 

The  heliographic  process  in  which  silver  salts  are  the  sensitive 
elements,  although  an  invention  of  a  later  day  than  the  Herschel-type, 
is  the  oldest  process  of  this  kind  adopted  by  architects  and  engineers 
for  copying  drawings.  For  this  reason  we  will  first  treat  of  this  pro- 
cess. It  was  first  practically  introduced  by  Romain  Talbot,  and  has 
been  taught  as  a  regular  subject  of  instruction,  by  Prof.  Vogel,  at  the 
Berlin  Polytechnic  High  School,  since  the  autumn  of  1870.  During  the 
winter  of  1872-73,  the  number  of  students  who  took  instruction  in  the 
art  of  sun-drawing,  from  Prof.  Vogel,  was  as  high  as  sixty. 

Romain  Talbot  mentions  —  in  a  price-list  which  bears  the  date  March, 
1873  —  757  firms,  offices,  architects,  engineers,  artists  and  scientists,  who 
had  ordered  sensitive  paper  and  apparatus,  for  this  purpose,  from  him. 

1.  The  Salts  of  Silver, 

used  in  solar  printing,  and  which  we  will  consider  in  order,  are : 

Chloride  of  Silver,  Iodide  of  Silver, 

Bromide  of  Silver,  Nitrate  of  Silver. 

Chloride  of  Silver,  Ag  CI  or  Ag2  Cl2. —  Chloride  of  silver  occurs, 
in  nature,  as  a  rare  mineral,  of  yellowish-gray  color,  and  is  then  known 
as  horn  silver.  It  is  found  in  Mexico  and  Peru,  as  also  in  Saxony  and 
Siberia.  As  early  as  the  year  1546,  Fabricius  noticed  that  horn  silver 
turned  black  in  the  light.  The  first  remark,  in  reference  to  the  cause  of 
the  change  of  color  in  silver  salts,  is  due  to  the  distinguished  Swedish 
chemist,  Scheele,  in  1777.  Artificially,  chloride  of  silver  is  precipitated 
as  a  white,  curdy  mass,  when  solutions  of  a  chloride  and  of  a  silver 
salt  are  brought  together.  If  this  white  precipitate  is  kept  in  the  dark, 
it  will  remain  white  for  an  unlimited  time;  but  when  exposed  to  sun- 
light, the  white  chloride  becomes  tinted  with  a  purple  color,  which  will 
increase  in  depth  as  the  action  of  the  light  continues.  It  is  decom- 
posed by  solutions  of  the  caustic  alkalies — which  convert  it  into  oxide — 
but  not  by  the  carbonates.  After  the  formation  of  the  oxide,  in  this 
way,  the  addition  of  sugar  reduces  it  and  revives  the  silver  (Levol). 
Chemically,  chloride  of  silver  is  a  compound  of  two  elements,  metallic 
silver  and  chlorine.  Both  elements  appear  to  be  but  loosely  compounded, 
as  the  influence  of  light  partially  decomposes  the  chloride  of  silver — 
both  in  the  dry  and  in  the  wet  state — very  slowly  if  pure,  and  quickly 

27 


* 


28 


MODERN  HELIOGRAPHIC  PROCESSES. 


if  organic  matter  be  present;  free  chlorine  gas  is  given  off,  and  a 
compound  containing  less  chlorine  is  left  behind.  This  last  compound 
is  not  white,  but  of  a  violet-black  color.  When  the  white,  precipitated 
chloride  is  heated,  it  melts,  and,  on  cooling,  becomes  a  grayish,  crystal- 
line mass,  which  cuts  like  horn,  constituting  the  mineral  called  horn 
silver. 

Iodide  op  Silver,  Ag  I  or  Ag2  I2. — Iodide  of  silver  is  also  a  com- 
pound of  two  chemical  constituents,  metallic  silver  and  iodine.  It  is  a 
grayish  or  bluish-black  solid,  of  a  metallic  luster,  somewhat  resembling 
plumbago.  When  freshly  prepared,  it  has  a  yellow  color.  This  com- 
pound is  obtained  by  pouring  a  solution  of  iodide  of  potassium  into  a 
solution  of  nitrate  of  silver;  it  will  then  be  precipitated  as  a  yellow 
powder. 

In  preparing  chloride  of  silver,  for  photographic  purposes,  it  is  im- 
material in  what  order  the  solutions  are  mixed;  whether  the  chloride 
is  poured  into  the  silver  solution,  or  vice-versa,  the  result  will  be  the 
same  and  have  the  same  properties.  Not  so  in  the  preparation  of  the 
iodide  of  silver;  here  it  is  very  important  to  mix  the  solutions  in  the 
right  order.  If  the  silver  solution  is  poured  into  the  iodide  of  potas- 
sium solution — and  not,  as  above  stated,  the  iodide  of  potassium  into 
the  silver  solution — the  precipitate  will  be  lighter  in  color,  nearly  white, 
and,  what  is  most  remarkable,  will  not  be  affected  by  light. 

Bromide  of  Silver,  Ag  Br  or  Ag2  Br2. —  Silver  bromide  occurs,  native, 
in  Chili  and  Mexico,  as  bromargyrite,  usually  in  small  yellow  or  greenish 
masses;  also,  mixed  with  the  chloride,  as  embolite.  It  is  obtained,  on 
adding  a  bromide  of  an  alkali-metal  to  a  solution  of  nitrate  of  silver, 
as  a  white,  curdy  precipitate.  When  suspended  in  water,  it  is  easily 
decomposed  by  chlorine.  The  fused  bromide  is  scarcely  acted  upon  by 
light,  but  the  precipitated  bromide,  when  exposed  to  light,  quickly 
assumes  a  grayish-white  color. 

Nitrate  of  Silver,  Ag  N  03. —  Silver  nitrate  is  obtained  by  dis- 
solving metallic  silver  in  nitric  acid  and  evaporating  the  solution  to 
dryness,  or  until  it  is  strong  enough  to  crystallize  on  cooling.  The 
crystals  are  colorless,  transparent,  anhydrous  tables.  For  pharmaceutical 
purposes,  the  crystals  are  fused  and  poured  in  silver  molds  of  the  size 
of  a  goose-quill.  In  this  form,  it  is  known  as  lunar  caustic  or  lapis 
infernalis.  For  heliographic  purposes,  the  crystallized  salt  should 
always  be  used.  The  nitrate  of  silver  is,  in  itself,  not  sensitive  to 
light,  but  it  becomes  so  if  brought  in  contact  with  organic  sub- 
stances. For  example,  a  piece  of  paper  saturated  with  a  solution  of 
this  salt,  quickly  becomes  brown  in  the  light,  and  finally  black.  One 
drop  of  the  solution  placed  on  the  skin,  or  on  white  linen,  will  leave  a 
fixed  spot. 


SILVER  PRINTS  PERMANENT  CHLORIDE  OF  SILVER  PAPER. 


29 


2.  Permanent  Sensitive  Chloride  of  Silver  Paper. 

The  prepared  albumen  or  arrow-root  paper  of  commerce  contains  a 
certain  quantity  of  a  soluble  chloride,  chiefly  sodium  chloride,  Na  CI 
(common  salt),  or  chloride  of  ammonium,  H4  N  CI  (sal-ammoniac)  ;  so 
that  this  paper,  in  order  to  be  sensitized,  needs  only  to  be  brought  in 
contact  with  a  solution  of  silver  nitrate  to  form,  in  the  paper,  chloride 
of  silver,  and  to  impart  to  it,  without  any  other  manipulation,  a  high 
degree  of  sensibility  to  light. 

Plain  writing  or  drawing  paper  must  first  be  impregnated  by  a 
solution  of  such  a  soluble  chloride  before  being  sensitized.  For  this 
purpose,  we  immerse  the  paper  in  a  filtered  solution  of 

Common  Salt,    ....      1  part.  ) 
Water,  30  parts. 

It  is  very  important  that  the  paper  be  uniformly  moistened.  Air- 
bubbles  must  at  once  be  removed  with  a  glass  rod  or  a  wooden  stick. 
After  about  two  minutes,  the  paper  is  taken  out  of  the  bath,  and  hung 
up  to  dry.  The  surplus  of  the  salt  lye  must  be  removed  by  pressing  the 
lower  edge  of  the  sheet  between  two  sheets  of  clean  blotting  paper. 

When  paper,  thus  prepared,  is  brought  in  contact  with  the  solution 
of  silver  nitrate,  the  soluble  chloride,  in  the  papoj,  is  converted  into 
the  insoluble  chloride  of  silver,  and,  at  the  same  time,  a  certain  amount 
of  the  nitrate  of  silver  solution  is  absorbed  by  the  paper. 

Paper  which  was  only  saturated  by  a  solution  of  silver  nitrate,  will 
be  found  to  be  a  great  deal  less  sensitive  to  light  than  that  which 
contains  chloride  of  silver  also. 

Professional  photographers  usually  buy  the  salted  albumen  paper, 
and  do  the  sensitizing,  printing  and  fixing  all  in  one  day. 

The  sensitized  silver  paper  offered  in  the  market,  for  copying  draw- 
ings and  the  like,  differs  from  that  prepared  by  the  professional  pho- 
tographer in  as  much  as  it  can  be  preserved  for  a  considerable  time, 
either  before  printing,  or  between  printing,  toning  and  fixing.  This  is 
a  great  convenience  for  the  draughtsman,  who  engages  the  light  as  his 
assistant,  for  copying  his  drawings,  etc.  Photographers  do  not  think 
very  much  of  this  sensitized  paper,  because  the  beautiful  violet  or 
purple  tone  can  not  be  produced  upon  it. 

The  sensitized  chloride  of  silver  paper  of  the  market,  is  mostly 
glossy  albumen  paper.  The  largest  sheets  are  18"X  22",  and  cost  about 
$3.00  per  dozen.  For  technical  drawings,  we  often  need  larger  sheets, 
and  plain  and  heavier  paper,  which  does  net  curl  like  unmounted 
albumen  paper,  is  often  preferable.  Therefore,  we  will  now  endeavor  to 
explain  what  we  have  learned,  concerning  the  preparation  of  durable 
silver  paper,  from  the  works  of  Vogel,  Haugk,  Liesegang  and  others. 


30 


MODERN  HELIOGRAPHIC  PROCESSES. 


The  preparation  of  such  paper  was,  until  recently,  a  trade  secret;  but 
the  teachers  of  the  light-drawing  processes  have  revealed  a  great  deal — 
if  not  the  whole  —  of  the  secret. 

Mr.  A.  Ost,  of  Vienna,  found  a  method,  for  increasing  the  dura- 
bility of  silver  chloride  paper,  by  adding  citric  acid  to  the  solution  of 
silver  nitrate,  and  Mr.  Haugk,  by  first  washing  the  silvered  paper  in 
water,  and  then  fuming  it  with  ammonia,  shortly  before  exposing  it  to 
light.  By  washing  the  paper  in  water,  it  loses  a  large  part  of  its 
sensibility,  but  becomes  very  durable.  The  lost  sensibility  is  restored 
by  the  later  fuming  with  ammonia.    (According  to  Liesegang.) 

Paper  Prepared  with  Citric  Acid. — The  citro-silver  nitrate  solu- 
tion is  composed  of 


Plain,  salted  writing  or  drawing  paper  must  be  immersed  in  the  solu- 
tion. Albumen  and  arrow-root  paper  is  to  be  floated  upon  the  liquid 
with  the  coated  side  down. 

The  author  has  often  tried  to  silver  large  sheets  of  salted  paper 
with  a  tuft  of  cotton,  a  sponge,  or  a  brush,  but  without  success. 

For  each  square  inch  of  the  bottom  surface  of  the  pan,  1  fluid 
dram,  or  -J  fluid  ounce,  of  silver  salt  solution,  may  be  estimated,  as  a 
minimum  required,  provided  the  bottom  is  even.  The  depth  of  the 
liquid  will  then  be  \  inch,  and  it  may  be  used  until  but  one-half  of 
it  remains  in  the  pan. 

For  silvering  100  square  feet  of  paper,  about  1  ounce  of  nitrate  of 
silver  is  required,  or  4f  troy  grains  for  each  square  foot. 

•  A  room  lighted  by  a  lamp,  or  by  gaslight,  is  the  best  for  carrying 
on  the  sensitizing  process. 

A  small  piece  of  blotting  paper  should  be  caused  to  adhere  to  the 
lowest  edge  or  corner  of  the  sheet,  immediately  after  hanging  it  up  to 
dry.  The  blotting  paper  will  adhere,  by  capillary  attraction,  and  collect 
the  few  drops  of  solution,  which  would  otherwise  fall  on  the  floor.  If 
the  room  be  warm,  the  paper  will  dry  in  ten  or  fifteen  minutes. 

Paper  prepared  with  the  citro-silver  nitrate  solution,  will  remain, 
for  about  six  weeks  or  longer,  in  a  serviceable  condition,  but  it  must 
be  wrapped  up  in  several  sheets  of  paper  of  a  non-actinic  color,  and 
must  be  kept  in  a  perfectly  dark  and  dry  place. 

The  following  are  recipes  for  preparing  the  citro-nitrate  of  silver 
paper,  as  given  by  various  other  authorities : 


Nitrate  of  Silver, 
Distilled  Water,  . 
Citric  Acid,  .  . 
Alcohol,     .    .  . 


(2). 


SILVER  PRINTS  PERMANENT  CHLORIDE  OF  SILVER  PAPER. 


31 


/.  According  to  H.  Schuberth. — Take  thick,  salted  albumen  or  arrow- 
root paper,  and  let  it  float,  for  one  minute,  upon  the  following  bath: 


Distilled  Water,  ....  64  parts. 

Nitrate  of  Silver,     ...  6  parts. 

Citric  Acid,   2  parts. 

Tartaric  Acid,     .    .    .    .  1  part. 


(3). 


After  this,  the  paper  is  to  be  dried,  and  then  drawn  slowly  through 
water,  and,  finally,  dried  again. 

II.  According  to  Liesegang. —  Salted  albumen  or  arrrow-root  paper  is 
floated  upon  a  solution  of 

Nitrate  of  Silver,     ...     5  parts.  )  ,  ,v 

Distilled  Water  48  parts.  )  {  }' 

and  then  hung  up  to  dry.  Before  the  paper  is  perfectly  dry,  but  when 
it  no  longer  presents  a  shining  surface,  each  sheet  is  placed,  separately, 
between  blotting  paper,  and  weighted  down  by  means  of  a  heavy  board. 
When  perfectly  dry,  it  is  floated,  for  about  half  a  minute,  upon  a  solu- 
tion of 

Distilled  Water,  ...    720    parts.  \ 

Citric  Acid,     ....      15    parts.  >     ...  (5). 

Ammonia  Water,    .    .       3.7  parts.  ) 

It  is  then  dried  again,  between  blotting  paper,  and  preserved  in  the  dark. 

III.  According  to  Liesegang. —  The  salted  paper  is  sensitized  in  a 
solution  of 

Nitrate  of  Silver,    ...     1  part.   )  ,n\ 

Distilled  Water,  .    .    ,    .  12  parts.  )  \ 

When  quite  dry,  the  silvered  side  of  the  paper  is  treated  uniformly 
with  a  solution  of 

Citric  Acid,    .    .    ,    .    .      1  part.  ) 

Alcohol,   48  parts.  S  '  W- 

The  latter  solution  may  be  applied  with  a  sponge. 

IV.  According  to  Willis. — The  paper  is  floated  upon  a  solution  of 
Nitrate  of  Silver,    ...     1  part. 


Distilled  Water,  ....    10  parts.  v 

and,  when  nearly  dry,  the  drops  on  the  edges  are  absorbed  with  blotting 
paper,  and  then  the  paper  floated,  for  about  ten  seconds,  with  its  back 
upon  a  solution  of 


32 


MODERN  HELIOGRAPHIC  PROCESSES. 


Citric  Acid,  1  part.  ) 

Water,  15  parts.  ) 

When  dry,  this  paper  will  remain  unaltered  for  two  or  three  months, 
and  have  all  the  properties  of  freshly  sensitized  paper. 

V.  Monkhoveri's  Sensitizing  Solution. 

Nitrate  of  Silver,    ...    12  parts.  \ 

Nitrate  of  Magnesia.    .    .    12  parts.  >     .    .    .  (10). 

Distilled  Water,  ....  100  parts.  ) 

Every  time,  after  sensitizing  a  sheet  in  this  solution,  one  dram  of 
a  one-to-eight  solution  of  nitrate  of  silver  is  to  be  added  to  the  bath 
for  every  100  square  inches  of  paper  sensitized. 

Washed  Silver  Paper. — Washed  silver  paper  is  prepared  in  a  sim- 
ilar manner.  The  sensitizing  solution,  however,  contains  no  citric  acid, 
and  merely  consists  of 

Nitrate  of  Silver,     ...      1  part.  ) 
Distilled  Water,  ....    12  parts.  )     '  ' 

As  soon  as  the  paper  is  lifted  out  of  this  silver  bath,  and  before  it 
is  hung  up  to  dry,  it  is  washed  several  times. 

For  this  purpose,  two  sufficiently  large  trays  are  filled  with  water, 
and,  as  soon  as  a  sheet  is  taken  from  the  silvering  bath,  it  is  immersed 
in  the  water  in  the  first  pan,  turned  over  several  times,  and  then  placed 
in  the  second  pan. 

After  a  number  of  sheets  have  been  silvered,  and  passed  from  the 
first  to  the  second  tray,  the  water  in  the  first  pan  is  renewed,  and  then 
the  sheets,  one  by  one,  are  returned  to  the  first  pan,  turned  over  a  few 
times,  and  hung  up  to  dry. 

By  this  repeated  washing,  the  paper  is  rendered  exceedingly  durable, 
but,  at  the  same  time,  in  the  same  degree,  less  sensitive  to  light.  The 
sensitiveness  can,  however,  be  restored  by  exposing  the  paper  to  the 
fumes  of  strong  ammonia. 

The  washed  silver  paper  may  be  preserved  for  years,  in  good  con- 
dition, if  it  is  kept  in  a  dark  place,  and  wrapped  in  yellow  paper. 

Fuming  with  Ammonia. —  Instead  of  fuming  the  washed  silver  paper 
itself,  it  is  more  effective  to  fume  the  blankets,  or  pads  of  paper,  which 
come  in  contact  with  the  sensitive  paper,  in  the  printing  frame.  For 
this  fuming  process,  a  tight-closing  box  is  required,  which  must  be 
provided  with  a  false  bottom,  consisting  of  a  coarse  net-work  made  of 
cane  or  bast,  and  placed,  in  such  a  manner  that  it  can  be  easily 
removed,  one-half  to  one  inch  from  the  real  bottom.     Upon  the  real 


SILVER  PRINTS  ORDINARY  CHLORIDE  OF  SILVER  PAPER. 


33 


bottom,  one  or  more  plates  or  dishes  (according  to  the  size  of  the  box), 
containing  strong  ammonia,  are  placed ;  then  the  false  bottom  is  put 
into  the  box,  and,  upon  it,  the  blankets.  The  latter  are  to  be  turned 
over  several  times,  and  kept  in  the  fuming  box  until  they  are  thoroughly 
impregnated,  and  smell  strongly  of  ammonia.  The  more  ammonia  vapors 
the  blankets  have  absorbed,  the  more  brilliant  the  prints  will  be. 

If  engravings  or  drawings  are  to  be  reproduced,  which  are  made  on 
thick  paper,  and  which  will  require  a  long  exposure  to  light,  it  becomes 
necessary  to  paste  the  sensitive  paper,  at  two  corners,  to  the  original, 
or  to  provide  other  means,  so  that  the  blankets,  or  paper  pads,  may  be 
taken  out  and  replaced,  by  freshly  fumed  ones,  without  moving  the 
sensitive  paper  out  of  place.  The  renewal  of  the  fumed  blankets  is 
requisite,  if  the  time  of  exposure  is  long,  since  a  part  of  the  ammonia 
will  volatilize  unused. 

3.  Ordinary  Chloride  of  Silver  Paper. 

Plain  salted  paper  is  immersed  in,  albumen  or  arrow-root  paper 
floated  upon,  a  silver  solution  of 

Nitrate  of  Silver,    ...    10  parts.  ) 

Distilled  Water,  ....  100  parts.  )  '  { 

An  acid  reaction  of  this  bath  makes  the  paper  more  durable,  but 
difficult  to  tone  in  the  gold  bath.  Therefore,  it  is  recommended,  for 
prints  on  albumen  paper,  which  are  intended  to  be  toned,  to  make 
the  silver  bath  neutral,  or  weakly  alkaline,  by  adding  to  it,  drop  by 
drop,  a  solution  of  carbonate  of  soda,  or  bicarbonate  of  soda,  in  ten 
parts  of  water,  until  a  white,  flaky  precipitate  of  carbonate  of  silver 
commences  to  form.  This  white  precipitate  is  to  be  left  in  the  bottle, 
and  not  removed  in  filtering.  If  the  salt  solution  contains  starch 
(arrow-root  or  tapioca),  or  some  gelatine,  the  liquid  will  not  soak  so 
deeply  into  the  paper,  as  without  this  addition.  It  will  cause  the  photo- 
graphic picture  to  remain  on  the  surface  of  the  paper,  and  present  a 
finer  and  more  delicate  appearance. 

Preparation  of  Paper  with  Arrow-Root. —  For  the  preparation  of 
arrow-root  paper ',  the  following  approved  recipes  will  serve : 

According  to  Monkhoven. 

Water,  

Chloride  of  Sodium, 
Citrate  of  Sodium,  . 
Arrow-root,      .    .  . 


100  parts. 
2  parts. 
2  parts. 
2  parts. 


•  (13). 


34 


MODERN  HELIOGRAPHIC  PROCESSES. 


According  to  Vogel. 

Water,  100    parts.  \ 

Chloride  of  Sodium,  .    .     2    parts.  >     .    .    .  (14). 

Arrow-root,  3-J  parts.  ) 


According  to  Kleffel. 

Water,   100  parts 

Chloride  of  Ammonium,  1  part 

Arrow-root,   3-J 

Citric  Acid,   ^  part, 


■1 


•  (15). 


The  arrow-root  flour  is  to  be  stirred  and  thoroughly  mixed  with 
some  cold  water,  and  then  poured,  while  constantly  stirring,  into  the 
boiling  water. 

According  to  Liesegang,  tapioca  may  be  substituted  for  the  arrow- 
root. The  paper  is  coated  with  the  starch  mixture,  by  means  of  a 
brush,  first  going  over  the  paper,  in  parallel  strokes,  in  two  directions, 
and  then  moving  the  brush  in  small  circles,  so  as  to  equalize  the 
coating. 

Arrow-root  paper  should  not  be  floated,  on  the  silver  bath,  longer 
than  -J  to  1  minute.  If  the  silvering  be  continued  too  long  (3  minutes), 
the  prints  frequently  become  gray. 

A  fuming  of  the  arrow-root  paper,  for  about  8  minutes,  in  the 
ammonia  box,  shortly  before  printing,  will  make  the  prints  more  in- 
tense—  darker  and  more  brilliant. 

Preparation  of  Paper  with  Gelatine. — Abney  recommends,  for 
prints  on  dull  paper : 

First  Recipe. 

Water,   480  parts.  ^ 

Chloride  of  Ammonium,  .  6-8  parts. 

Gelatine,  1  part.    >   .    .    .  (16). 

Citrate  of  Sodium,  ...    10  parts. 
Chloride  of  Sodium,    .    .  2-3  parts.  J 


Second  Recipe. 

Water,   480  parts.  \ 

Chloride  of  Ammonium,  .    10  parts.  >     .    .    .  (17). 
Gelatine,  1  part.  ) 

The  gelatine  is  first  dissolved  in  the  water  by  heating,  then  the  salts 
are  added,  the  solution  filtered,  and  the  paper  floated  on  the  same. 


SILVER  PRINTS  ORDINARY  CHLORIDE  OF  SILVER  PAPER.  35 

Preservation  of  the  Ordinary  Chloride  of  Silver  Paper. —  Paper 
sensitized  without  citric  acid,  and  not  washed,  may  be  preserved,  for 
some  time,  by  placing  it  between  blotting  paper  that  has  been  satu- 
rated with  a  solution  of  bicarbonate  of  potash  and  then  dried. 

If  kept  in  a  perfectly  dry  place,  paper  prepared  without  citric  acid, 
and  not  washed,  will  also  remain  in  a  good  condition  for  a  long  time. 
For  this  purpose,  a  box,  closing  air-tight,  and  having  two  compartments 
(for  example,  two  drawers),  one  above  the  other,  is  used.  The  lower 
compartment  contains  calcium  chloride,  or  freshly  burnt  lime,  the  upper 
one,  which  has  a  perforated  bottom,  contains  the  paper. 

In  such  a  box,  the  paper  will  remain  white  for  months;  but,  before 
using  the  paper,  it  should  be  brought  to  a  damp  place,  for  a  short 
time,  so  as  to  take  up  a  little  moisture,  since  perfectly  dry  chloride  of 
silver  paper  is  not  sensitive  to  light. 

4.  How  Long  to  Expose  Silver  Prints. 

Silver  prints  must  be  printed  considerably  darker  than  they  are 
required  to  be  when  finished.  The  exact  amount  of  intensity  lost,  in 
the  finishing  processes,  can  only  be  learned  by  experience;  but  we  may 
say,  approximately,  that  it  is  necessary,  in  order  to  insure  a  satisfactory 
copy,  to  print  for  about  twice  as  long  a  time  as  that  required  to  give 
a  pleasing  result  in  the  frame. 

5.  Fixing  Silver  Prints. 

The  image  obtained,  by  the  direct  agency  of  light,  has  a  beautiful 
color,  but  the  picture  is  not  permanent,  for  light  still  continues  to  act 
upon  the  prepared  film,  and  finally  obliterates  the  image.  The  prints 
obtained,  when  taken  out  of  the  copying  frame,  must  be  made  light- 
resisting,  or,  as  the  photographer  says,  they  must  be  fixed. 

The  first  attempts  to  copy  drawings,  engravings  and  flat  bodies,  such 
as  leaves  of  plants,  by  means  of  light,  were  made  by  Wedgwood  and  by 
Sir  Humphrey  Davy,  at  the  beginning  of  this  century.  Unfortunately, 
these  prints  were  not  durable.  They  had  to  be  kept  in  the  dark,  and 
could  only  be  exhibited  in  subdued  light.  If  they  remained  exposed 
to  light  for  any  length  of  time,  the  white  parts  also  became  black,  and 
the  picture  disappeared.  No  means  were  then  known  for  making  the 
image  durable  —  that  is  to  say,  light-resisting. 

Not  until  sixteen  years  later  were  such  means  discovered,  in  the 
hyposulphite  of  soda,  by  Sir  John  Herschel,  who  herewith  completed 
the  invention  of  heliography.  Notwithstanding,  the  discovery  of  Herschel 
remained  as  good  as  unknown  until  1839,  when  Fox  Talbot  made  use 
of  it  in  one  of  his  inventions. 

The  fixing  must  also  be  done  in  weak  light.  Each  impression  may 
be  fixed  immediately  after  having  been  taken  out  of  the  printing  frame. 


36 


MODERN  HELIOGRAPHIC  PROCESSES. 


It  is  more  profitable,  however,  to  keep  the  proofs  in  a  dark  place  until 
a  desired  number  has  been  printed,  and  then  fix  all  of  them  at  the 
same  time. 

The  prints  are  taken,  one  by  one,  and  placed  in  a  suitable  dish, 
containing  clean  water.  They  are  immersed  in  the  water,  turned  over, 
immersed  and  turned  over  again,  and  moved  about  with  the  hand.  It 
will  then  be  seen  that  the  water  becomes  milky  if  unwashed  chloride 
of  silver  paper  has  been  used.  The  water  must  be  changed  a  few  times, 
until  this  milkiness  disappears  almost  entirely.  The  prints  are  then 
removed  from  the  water,  and  placed  in  another  flat  dish,  containing  a 
sufficient  quantity  of  a  solution  of  hyposulphite  of  soda.  They  are  kept 
moving  about  in  this  for  10  or  20  minutes,  but  should  not  remain 
too  long  in  this  fixing  bath.  If  the  white  parts  of  a  print  are  full  of 
gray  spots,  as  may  be  seen  when  held  up  to  the  light,  the  fixing  is 
incomplete;  but  if  all  these  spots  have  disappeared,  the  fixing  may  be 
considered  as  complete. 

Similar  gray  spots  will  also  appear  if  the  sheets,  at  any  time  be- 
tween the  first  washing  and  fixing,  were  exposed  to  strong  sunlight. 
Therefore,  all  operations,  until  the  fixing  is  complete,  ought  to  be  carried 
on  in  feeble  light. 

The  fixing  solution  is  composed  of 

Hyposulphite  of  Soda,  .    .    1  part.  ) 

Water,  6  parts,  i     .    .    .  (18). 

Aqua  Ammonia,   .    .    .    .    -J  part.  ) 

The  last  is  not  absolutely  necessary,  and  may  be  omitted  if  not  on 
hand. 

A  little  attention  is  required  in  handling  the  fixing  salt,  or  a  solu- 
tion of  the  same.  If  the  fingers  have  been  in  contact  with  this  salt, 
they  will  produce,  on  silvered  paper,  or  on  prints  not  yet  fixed,  unavoid- 
able brown  spots. 

The  hyposulphite  of  soda  exhibits  its  fixing  power  only  when  a  large 
quantity  of  it  is  brought  in  contact  with  the  prints. 

6.  Washing  Fixed  Silver  Prints. 

After  fixing,  it  is  necessary  to  wash  the  prints  thoroughly.  This 
is  best  done  in  running  water;  but,  if  this  can  not  be  had,  the  water 
used  must  frequently  (from  6  to  8  times)  be  renewed.  After  a  little 
practice,  the  washing  process  will  not  take  longer  than  half  an  hour. 
It  is,  however,  important  to  remove  the  hyposulphite  of  soda  completely, 
as  the  least  trace  of  this  salt,  that  may  remain  in  the  prints,  will  cause 
them  to  fade. 

The  simplest  and  most  reliable  method  of  ascertaining  whether  the 
prints  have  been  washed  sufficiently,  is  the  following: 


SILVER  PRINTS  WASHING  FIXED  SILVER  PRINTS. 


87 


Prepare  a  solution  of 

Iodine,  

Iodide  of  Potassium, 
Water,  

and  also  a  solution  of 

Starch,  1  part.    )  ^q) 

Boiling  Water,    ....  100  parts.  )  '  [  h 

Then  mix  the 

Iodine  Solution  (19),     .    .     1  part.    )  /^i  \ 

With  the  Starch  Solution  (20),  1  part.   S  '  * 

When  cool,  a  blue  liquid  will  be  obtained,  which  is  easily  discolored  by 
hyposulphite  of  soda.  The  blue  iodide  of  starch  may  be  preserved  for 
weeks,  if  a  few  drops  of  a  solution  of  carbolic  acid  are  added. 

In  order  to  test  the  rinsing  water  for  hyposulphite  of  soda,  half 
fill  two  test-tubes  with  the  blue  starch  solution.  Dilute  one  of  them 
with  pure  water,  and  the  other  with  the  last  washing  water.  If  the 
second  test-tube  contains  hyposulphite  of  soda,  it  will  at  once  be  per- 
ceived, by  the  more  or  less  complete  discoloration  of  the  solution,  in 
comparison  with  the  color  of  the  contents  of  the  other  test-tube. 

For  fixing  and  washing  silver  prints,  japanned  tin,  or  wooden,  trays 
(the  latter  coated  with  asphaltum  varnish),  may  be  used. 

7.  Toning  Silver  Prints. 

When  prints  are  removed  from  the  first  rinsing  water,  and  immersed 
in  the  fixing  bath,  they  undergo  a  disagreeable  change  in  color.  The 
fainter  the  copies  have  been  printed,  the  more  disagreeable  this  change 
in  color  will  be.  In  drawings  for  technical  purposes,  this  change  is 
of  no  consideration;  but  in  copies  of  fine  drawings,  and  in  reproduc- 
tions of  engravings,  and  pictures  with  half  tints,  the  unpleasing  tone 
is  objectionable. 

In  order  to  give  a  more  agreeable  tint  to  such  pictures,  they  are 
plunged,  before  fixing,  into  a  solution  of  chloride  of  gold.  This  is  called 
the  toning  process. 

The  toning  bath,  for  prints  on  citro-chloride  of  silver  paper,  is  com- 
posed of 

Distilled  Water,  .  .  20,000  parts. 
Fused  Acetate  of  Soda,  100  parts. 
Chloride  of  Lime,  ...  ^  parts. 
Chloride  of  Gold,  .    .    .  -J-f  parts. 

and  is  to  be  used  lukewarm. 


1  part.  \ 
20  parts.  [     .    .    .  (19). 
600  parts.  ) 


38 


MODERN  HELIOGRAPHIC  PROCESSES. 


For  copies  on  washed  chloride  of  silver  paper,  the  following  solu- 
tion is  recommended : 

Water,  ....  1,500-1,800    parts.  \ 

Carbonate  of  Magnesia,  .    1    part.   V    .    .    .  (23). 

Chloride  of  Gold,    ...    1^-  parts.  ) 

This  solution  must  be  shaken  frequently,  and,  after  about  3  hours, 
filtered,  when  it  will  be  ready  for  use.    It  is  to  be  used  cold. 

After  the  prints  have  been  washed,  and  before  fixing,  they  are  put 
in  the  gold  bath,  but  not  more  than  three  or  four  at  a  time. 

Take  one  print  from  the  rinsing  water,  and  place  it  in  the  toning 
solution,  at  first  face  downward,  and  then  turn  it  face  upward.  Turn  it 
over  in  this  manner  several  times,  so  as  to  allow  the  gold  solution  to 
act  equally  in  all  parts.  Now  take  another  print — or,  perhaps,  three  or 
four — and  place  it  in  the  solution  in  the  same  manner  as  the  first.  It 
will  be  noticed  that  the  prints,  during  washing,  have  changed  their 
color;  some  will  become  of  a  brick-red.  In  the  toning  bath,  they  will 
change  to  a  brown,  and  gradually  to  a  sort  of  violet  or  purple.  They 
must  be  constantly  kept  in  motion.  The  best  plan  is  to  continually 
remove  the  undermost  print  and  place  it  on  top.  At  first,  only  one  or 
a  few  prints,  according  to  the  size,  should  be  attempted;  after  some 
practice,  more  may  be  undertaken.  Professional  photographers  are  able 
to  handle  several  dozen  prints,  in  the  toning  bath,  at  the  same  time. 
When  many  prints  are  toned  together,  it  is  a  good  plan  to  have  two 
dishes  of  toning  solution,  side  by  side,  and  lift  the  sheets  out  of  one 
into  the  other,  and  when  they  are  all  in  one  dish,  to  turn  them  over 
in  a  mass. 

The  longer  the  prints  are  left  in  the  gold  bath,  the  more  marked 
will  be  the  change  of  their  color,  especially  those  on  washed  paper. 
Prints  on  citro-chloride  of  silver  paper — for  which  a  toning  bath  accord- 
ing to  formula  (22)  is  used  —  should  remain  in  the  bath  until  they  have 
a  violet-black,  or,  at  least,  a  deep  chocolate-brown,  color. 

Prints  on  washed  paper  will  change  in  the  gold  solution  (23)  from 
a  light  sepia-brown  to  a  brownish  violet  and  black  color.  The  deepest 
tint  will  only  result,  after  fixing,  in  a  beautiful  dark  color  if  the  prints 
were  copied  very  dark.  If  this  was  not  the  case,  the  finished  prints 
will  be  of  a  pale,  blue-gray  color.  Therefore,  it  is  better  to  take  such 
prints  out  of  the  toning  bath,  when  they  have  reached  the  brownish-violet 
tone.  Prints  which  were  taken  out  of  the  gold  bath  too  soon,  will  look 
fox-brown  when  finished. 

When  the  prints  have  passed  through  the  toning  bath,  and  obtained 
the  required  tone,  they  are  plunged  into  water — whereby  the  process  is 
interrupted  —  and  then  fixed  in  the  same  manner  as  if  they  had  not 
been  toned. 


SILVER  PRINTS  WITH  DEVELOPMENT. 


39 


It  does  not  injure  the  prints  to  immerse  them  in  the  fixing  bath 
immediately  after  having  been  taken  out  of  the  toning  bath,  but  care 
must  be  taken  that  no  hyposulphite  gets  into  the  gold  bath,  as  this 
will  destroy  the  toning  action  and  produce  yellow  spots  in  the  prints. 
One  grain  of  gold  is  amply  sufficient  for  400  square  inches  of  prints. 

8.  Liesegang's  Combined  Toning  and  Fixing  Bath. 

Two  solutions  are  made ;  the  first  consisting  of 

Rain  Water,   1,000  parts. 

Hyposulphite  of  Soda,   250  parts. 

Sulphocyanide  of  Ammonium,  .  .  25  parts. 
Acetate  of  Soda  (Crystallized),  .    .      15  parts. 

and  the  second,  of 

Rain  Water,      ....    100  parts.  ) 
Chloride  of  Gold,  ...       1  part.   )     '    '    '  K*°h 

The  second  solution  is  poured  into  the  first,  but  not  the  reverse,  as 
the  gold  would  otherwise  be  separated  from  it. 

The  prints,  after  having  been  taken  out  of  the  printing  frame,  are 
washed  in  water,  and  then  placed  in  this  bath  and  turned  over  several 
times.  The  tone,  at  first,  becomes  a  yellowish-brown,  then  a  darker 
brown,  and,  finally,  a  beautiful  black.  When  the  desired  color  has  been 
obtained,  the  prints  are  to  be  taken  out  of  the  bath  and  thoroughly 
washed  in  water,  as  stated  on  page  36. 

9.  Silver  Prints  with  Development. 

The  following  rapid  printing  process  is  said  to  have  been  used, 
during  the  last  Franco-German  war,  for  copying  maps. 

The  most  suitable  paper  for  this  process  is  Steinbach's  heliographic 
paper.    The  paper  is  first  coated  with  the  following  preparation: 

Iodide  of  Potassium,  .    .     1  part.  \ 

Chloride  of  Potassium,    .     4  parts.  >     .    .    .  (26). 

Distilled  Water,  ....  100  parts.  ) 

Filter  the  solution,  and  then  pour  it  into  a  porcelain  jar,  and  mix 
with  it  2  parts  of  the  finest  arrow-root  flour.  Then  heat  the  mixture, 
while  continually  stirring  it  with  a  glass  rod,  to  the  boiling  point.  Let 
it  cool  again,  and  remove  the  scum  formed  upon  the  surface. 

Apply  the  preparation  cold,  and  as  uniformly  as  possible,  to  the 
paper,  by  means  of  a  camel's-hair  brush.  In  a  closed  portfolio,  paper 
so  prepared  may  be  preserved  for  several  days.    If  it  should  turn  light- 


40 


MODERN  HELIOGRAPHIC  PROCESSES. 


red,  or  if  marble-like  spots  should  appear  on  its  surface,  it  ought  not 
to  be  condemned  on  that  account.  The  paper  is  sensitized  by  floating 
it  upon  the  following  bath: 

Distilled  Water,  ....  100  parts.  \ 

Nitrate  of  Silver,    ...     8  parts.  >     .    .    .  (27). 

Citric  Acid,  -J  part.  ) 

Paper  thus  prepared  is  extremely  sensitive,  and  must  not  be  brought 
into  strong  light  for  a  single  moment.  It  must  be  placed  in  the  copy- 
ing frame,  in  yellow  light. 

The  rapid  action  of  the  light  is  not  apparent  at  once.  The  exposure 
is  complete  when  the  outlines  of  the  drawing  are  but  faintly  marked. 
After  having  been  taken  out  of  the  copying  frame,  the  print  is  floated, 
face  downward,  on  a  developing  solution  of 

Gallic  Acid,  1  part.  ) 

Distilled  Water,  ....  500  parts.  )  '  *  . 

In  this,  the  picture  will  gradually  develop  of  a  dark-brown  color. 
When  sufficiently  distinct,  it  is  to  be  dipped  into  clean  water,  in  order 
to  prevent  the  gallic  acid  from  penetrating  the  paper,  and  then  it  is 
either  fixed  at  once,  or  first  toned  and  then  fixed,  in  the  manner  we 
have  already  described.    All  this  is,  however,  to  be  done  in  yellow  light. 


10.  Talbot's  Calotype  Process. 


The  following  are  extracts  from  two  of  the  oldest  English  patents  on 
heliographic  printing  with  silver  salts: 

Extract  from  Patent  No.  884%,  of  Feb.  8,  18 41,  to  William  Henry  Fox  Talbot. 

The  first  part  of  the  preparation  of  the  paper  consists  in  washing 
one  side  with  a  solution  of 

Crystallized  Nitrate  of  Silver,    .  100  grains.  )  /qq\ 
Distilled  Water,  6  ounces.  ) 

drying  it,  and  then  dipping  it  in  a  solution  of 

Iodide  of  Potassium,   500  grains.  \ 


Water,  1  pint. 

keeping  it  there  a  minute  or  two,  then  dipping  it  in  water,  and,  after- 
ward, drying  it.  Paper  thus  prepared  will  keep  (if  not  exposed  to  the 
light)  any  length  of  time. 

The  second  stage,  which  is  best  left  until  the  paper  is  required  for 
use,  consists  in  washing  the  iodized  paper  with  gallo-nitrate  of  silver 
by  candlelight.      The  paper  is  then  dipped  in  water,  and,  when  dried, 


SILVER  PRINTS  TALBOT'S  CALOTYPE  PROCESS. 


41 


is  ready  for  use.  The  paper  thus  prepared,  termed  calotype  paper,  is 
placed  in  the  camera,  so  as  to  receive  an  image  from  the  lens,  the 
paper  being  screened  until  it  is  secured  to  its  place.  The  screen 
being  withdrawn,  an  image  is  formed  on  the  paper,  which  is  subse- 
quently developed  by  washing  the  paper  with  gallo-nitrate  of  silver,  and 
drying  it  before  a  gentle  fire.  The  fixing  process  consists  in  dipping 
the  picture  into  water,  partly  drying  with  blotting  paper,  and  washing 
it  with  a  solution  of 

Bromide  of  Potassium,  or  Common  Salt,    .    100  grains.  )  /r>-<  \ 

Water,  8-10  ounces.)  '  * 

The  picture  is  then  washed  with  water,  and,  finally,  dried.  The  picture 
thus  obtained  is  a  negative  one ;  that  is,  it  has  its  lights  and  shades 
reversed  with  respect  to  natural  objects  —  viz.,  the  lights  of  the  objects 
are  represented  by  shades,  and  vice-versa.  A  copy  of  this,  with  the 
natural  lights  and  shades,  is  obtained  by  placing  a  second  sheet  of 
sensitive  calotype  paper,  or  common  photographic  paper,*  in  close  con- 
tact with  the  paper  containing  the  picture,  putting  a  board  below  them 
and  a  plate  of  glass  above,  and  pressing  the  whole  together  by  screws. 
The  papers  thus  arranged  are  exposed  to  the  sun,  when  a  picture  with 
natural  lights  (a  positive  picture)  is  produced  on  the  second  sheet,  and 
developed  in  the  same  way  as  the  first. 

The  negative  picture,  when  rendered  faint  by  having  furnished  several 
copies,  may  be  revived  by  washing  it,  by  candle-light,  with  gallo-nitrate 
of  silver,  and  then  warming  it.  The  revived  picture  must  be  fixed  as 
before. 

2.  To  produce  a  positive  picture  by  a  single  process.  A  sheet  of 
calotype  paper  is  slightly  discolored,  by  exposure,  for  a  few  seconds,  to 
daylight.  It  is  then  dipped  in  a  solution  (as  above)  of  iodide  of 
potassium,  and  afterward  in  water,  lightly  dried  with  blotting  paper,  and 
placed  in  the  camera.  After  five  or  ten  minutes,  the  paper  is  withdrawn, 
and  washed  with  gallo-nitrate  of  silver,  and  warmed,  as  before  directed. 

An  image  will  then  appear  of  a  positive  kind  Engravings 

may  be  copied  in  the  same  way,  but  the  pictures  will  be  inverted.  The 
copy  may  be  strengthened  with  gallo-nitrate  of  silver  

Abridgment  of  English  Patent  No.  9753,  of  June  1,  1843,  to  W.  H.  Fox  Talbot. 
.  .  .  .  1.  Since  the  yellowish  tint  of  some  calotype  pictures  impedes 
the  process  of  taking  copies  from  them,  such  a  picture  is  plunged  into 
a  bath  of  some  soluble  hyposulphite,  whereby  it  is  rendered  white  and 
permanent.  Transparency  is  imparted  to  the  picture,  after  this  process, 
by  causing  melted  wax  to  penetrate  into  the  pores  of  the  paper. 

*"This  paper,"  the  patentee  observes,  "is  made  by  washing  good  writing  paper,  fir3t, 
with  a  weak  solution  of  common  salt,  and  then,  with  a  solution  of  nitrate  of  silver." 
This  had  been  freely  communicated  to  the  public  in  1839. 


42 


MODERN  HELIOGRAPHIC  PROCESSES. 


2.  During  the  process  of  taking  the  calotype  picture,  I  place  a  warm 
plate  of  iron  behind  the  paper-holder,  to  communicate  warmth  to  the 
prepared  paper.  This  makes  it  more  sensitive,  and,  consequently,  the 
picture  is  obtained  more  rapidly.  3.  Io-gallic  paper  is  prepared  by 
washing  a  sheet  of  iodized  paper  with  a  solution  of  gallic  acid  water, 
and  drying  it.  It  will  keep,  for  a  considerable  time,  in  a  press  or  port- 
folio. When  required  for  use,  it  is  rendered  sensitive  by  a  solution 
of  nitrate  of  silver,  and  fit  to  be  used  in  a  camera.  The  separate  use 
of  the  nitrate  of  silver  and  gallic  acid  removes  the  great  inconvenience 
arising  from  the  speedy  decomposition  of  the  gallo-nitrate  of  silver. 
4.  A  sheet  of  iodized  paper  is  washed  over  with  a  mixture  of  gallic 
acid  and  nitrate  of  silver,  usually  employed  in  the  calotype  process, 
and  dried  at  a  gentle  fire.  It  will  keep,  in  a  press,  for  a  considerable 
time.  It  is  less  sensitive  than  ordinary  calotype  paper.  This  paper  is 
as  convenient  to  use,  in  a  copying  frame,  as  the  ordinary  photographic 
drawing  paper,  it  being  used  quite  dry,  and  it  has  the  advantage  of 
being  much  more  sensitive.  5.  A  copy,  or  reversed  impression,  of  a 
photographic  picture  is  taken,  in  the  usual  way,  but  allowed  to  remain 
in  the  light  twice  the  usual  or  necessary  time,  in  consequence  of  which 
it  comes  out  with  its  shadows  too  black,  and  with  its  lights  not 
sufficiently  white  to  give  a  pleasant  effect.  It  is  then  washed,  and 
plunged,  for  1  or  2  minutes,  into  a  bath  of 


Iodide  of  Potassium,  .  500  grains. 
Water,   1  pint. 


(32). 


when  the  picture  becomes  brighter,  and  its  lights  a  pale  yellow  tint. 
The  effect  may  be  increased  by  exposure  to  light.  The  picture  is  then 
washed  and  plunged  into  hot  hyposulphite,  as  in  (1).  The  pale  yellow 
tint  is  thus  discharged,  and  the  lights  remain  of  a  white  color.  The 
picture  is  permanent,  and  has  a  pleasing  and  peculiar  effect  of  light 
and  shade,  not  easily  attainable.  6.  A  photographic  picture  is  rendered 
transparent  by  waxing  it,  and  a  sheet  of  white  or  colored  paper  placed 
behind  it,  so  as  to  produce  a  very  pleasant  artistic  effect,  or  various 

beautiful  tones  of  color  9  I  take  writing 

paper  of  a  good  quality,  destitute  of  water  mark,  and  dip  it  into  a 
salt  water  bath  containing 

Common  Salt,     .    .    .    3-4  ounces.  )  /r>o\ 
Water,   1  gallon.  )  '  * 

It  is  then  wiped  and  dried.    I  then  take  a  solution  of 

Nitrate  of  Silver,  .  .  100  grains.  ) 
Distilled  Water,  ...       2  ounces.  ) 


and  add  to  it  just  enough  ammonia  to  form  a  precipitate,  and  re-dissolve 


BROMIDE  OF  SILVER  EMULSION  PROCESS. 


43 


the  same,  leaving  the  solution  clear.  With  this  solution,  I  wash  the 
salted  paper  above  described,  and  then  dry  it.  Such  paper  may  be 
preserved  in  a  press,  but  should  be  used  within  1  or  2  days.  This  paper 
may  be  called  copying  paper.  To  obtain,  on  such  paper,  a  negative 
or  reversed  copy  of  any  print,  map,  photograph,  or  other  original 
on  paper,  it  is  placed  in  contact  with  the  original,  in  a  copying  frame, 
and  placed  in  the  daylight  until  the  copy  is  effected.  The  copy  is  then 
washed  with  warm  water,  kept,  afterward,  for  2  or  3  minutes,  in  a  solu- 
tion of  hyposulphite  of  soda  dissolved  in  10  times  its  weight  of  water, 
and  then  plunged  into  2  or  3  baths  of  warm  water,  consecutively,  in 
order  to  remove  all  that  is  soluble  in  water.  It  is  then  dried,  and 
may  be  waxed,  if  thought  proper,  for  greater  transparency.  A  good 
negative  picture  is  obtained,  with  a  camera,  upon  calotype  paper,  which 
is  then  cleaned  by  boiling  in  hyposulphite  of  soda,  and  waxed,  if 
thought  necessary.  The  negative  being  thus  prepared,  either  on  copying 
or  calotype  paper,  is  placed  in  contact  with  a  second  sheet  of  copying 
paper,  in  a  copying  frame,  and  a  positive  copy  obtained.  The  other 
positive  copies  are  similarly  obtained.  They  are  then  fixed,  with  hypo- 
sulphite of  soda,  in  the  same  way  as  the  negative  copy  was.  The 
hyposulphite  should  be  quite  free  from  sulphurous  acid,  and  the  copies, 
both  before  fixation  and  afterward,  should  be  dipped  into  2  or  3  warm 
water  baths,  consecutively,  to  remove  every  trace  of  soluble  matter 
from  them. 

11.  Bromide  op  Silver  Emulsion  Process. 

Paper  coated  with  bromide  of  silver  gelatine  emulsion — the  same 
substance  which  forms  the  sensitive  film  of  the  modern  instantaneous 
dry  plates  —  affords  a  means  for  copying  drawings,  writings,  etc.;  by 
lamplight  as  well  as  by  daylight,  even  when  the  originals  are  made  on 
bristol-board. 

Bromide  of  silver  paper  is  now  a  standard  trade  article,  used  by 
photographers  and  amateurs,  in  a  from  day  to  day  increasing  extent, 
for  contact-printing,  for  enlarging,  for  working  in  crayon,  india  ink, 
water  or  oil  colors. 

We  would  recommend  all  those  who  intend  to  try  this  paper,  and 
whose  time  is  much  occupied,  to  buy  the  paper  already  made.  East- 
man's Permanent  Bromide  Paper,  and  Anthony's  Gelatino-Bromide 
Rapid  Printing  Paper,  will  give  excellent  results.  They  are  cut  in  sheets 
of  various  sizes,  from  3i"X4i"  up  to  rolls  30"  wide  and  over  30  feet 
long,  and  cost  from  18  to  23  cents  per  square  foot.  Full  instructions 
accompany  each  package.  Several  varieties  of  this  paper  are  to  be  had : 
rough,  smooth,  thick,  or  thin.  For  copying  drawings,  etc.,  the  thin, 
smooth  paper  is  the  most  suitable.  There  is  also  a  paper  in  the 
market  especially  made  for  negatives. 


44 


MODERN  HELIOGRAPHIC  PROCESSES. 


For  the  benefit  of  those  engineers,  architects,  and  draughtsmen,  who 
are  fond  of  experimenting,  we  will  give  a  short  description  of  the 
preparation  of  the  bromide  paper,  and  a  few  formulae  for  the  emulsion. 

The  gelatino-bromide  paper  is,  as  the  dry  plates,  so  very  sensitive 
to  light,  that  a  drawing  on  bristol-board  can  be  copied,  in  from  6  to 
12  seconds,  by  holding  the  printing  frame,  in  which  the  sensitive  paper 
has  been  placed,  underneath  the  original  drawing,  about  14  inches  from 
a  gaslight,  or  from  the  flame  of  a  petroleum  (student's)  lamp. 

Ruby-colored  light  has,  fortunately,  not  such  a  great  effect  upon  this 
substance;  it  is  nearly  nonactinic.  Were  it  not  for  this  fact,  it  would 
be  impossible  to  cut  the  paper  and  place  it  in  the  printing  frame.  A 
room  that  can  be  made  perfectly  dark,  and  a  lantern  having  ruby-red 
glass,  or  glass  covered  with  paper  of  this  color,  are  indispensable  for 
preparing  silver  emulsions,  or  for  manipulating  with  paper  or  plates 
coated  with  the  same.  The  dark-room  lamp  must  be  so  constructed, 
that  not  one  ray  of  white  light  can  escape  from  it,  as  this  would  destroy 
the  sensitive  substance. 

After  the  paper  has  been  cut,  in  red  light,  and  placed  under  the 
original  drawing,  or  negative,  in  the  printing  frame,  it  is  best  to  expose 
to  gas  or  petroleum  light.  If  it  is  desirable  to  expose  to  daylight,  the 
frame  should  be  held  upside  down.  The  time  of  exposure  depends 
upon  the  intensity  of  the  light,  and  the  thickness  of  the  paper  on  which 
the  original,  tracing,  or  negative,  is  made.  Likewise,  the  emulsion  with 
which  the  paper  is  coated  may  also  be  made  more  or  less  sensitive. 

If  exposed  to  the  light  of  a  student's  lamp,  at  a  distance  of  about 
14  inches,  the  time  required  is,  in  general, 

5  to  10  seconds,  if  the  original,  or  negative,  is  made 
on  tracing  paper,  or  tracing  cloth. 

10  to  20  seconds,  for  originals  made  on  thin  writing 
paper. 

30  to  60  seconds,  if  the  light  has  to  pass  through 
thick  drawing  paper  or  through  bristol-board. 

In  order  to  obtain  good  prints,  the  originals  must  be  made  on 
paper  of  a  uniform  texture,  which,  if  examined  by  transmitted  light, 
shows  no  dark  spots. 

After  exposure,  the  printing  frame  is  placed,  upside  down,  on  a 
table,  and  quickly  covered  with  a  dark  cloth.  The  room  is  then  made 
dark  again,  and  the  frame  is  emptied  in  the  red  light  of  the  dark-room 
lamp.  The  print  may  now  be  developed  at  once,  or  it  may  be  pre- 
served in  a  book,  portfolio,  or  other  perfectly  dark  place,  for  hours  or 
days.    The  developing  must  also  be  done  in  red  light. 


BROMIDE  OF  SILVER  EMULSION  PROCESS. 


45 


Developing  and  Fixing  According  to  Romain  Talbot. — Three  solu- 
tions are  to  be  made : 


A.  —  Oxalate  of  Potash,  3  parts.  ) 

Boiling  Water,  10  parts.  S 

When  cool,  this  solution  is  to  be  filtered. 

B.  —  Protosulphate  of  Iron,  3  parts.  ^ 

Distilled  Water,  10  parts.  | 

Sulphuric  Acid  for  every  10  ounces 

of  Water,  1  drop. 


When  the  ferrous  salt  has  dissolved,  the  solution  is  filtered. 


(35). 


.  (36). 


1  part.  ) 

2  parts.  ) 


C. —  Citric  Acid,  ....... 

Distilled  Water,  

Also  to  be  filtered  when  dissolved. 

The  developing  bath  is  composed  of 


Solution  A,  15  volumes. 

Solution  B  5  volumes. 


.  (37). 


Solution  Cy 


1  volume 


.    .  (38). 


A  sufficient  quantity  of  the  mixture  is  then  poured  into  a  flat  tray 
(about  1  fluid  ounce  for  every  20  square  inches  of  bottom  surface  of 
the  tray).  Each  print  is  then  immersed  in  the  developing  bath,  avoid- 
ing air-bubbles  and  interruptions.  The  image  will  appear  in  a  short 
time;  but  it  should  not  appear  too  quickly,  as  this  is  a  sign  of  over- 
exposure. As  soon  as  the  picture  has  attained  the  desired  strength,  it 
is  taken  out  of  the  developer,  and  plunged  into  pure  water,  in  order  to 
arrest  further  development.  If  a  number  of  prints  are  to  be  developed, 
one  after  the  other  is  treated  in  the  same  manner.  If  the  developer 
becomes  too  weak,  it  may  be  strengthened  by  adding  some  of  the 
unused  mixture. 

For  the  fixing  bath,  two  solutions  are  made : 


A.  —  Hyposulphite  of  Soda,   4  parts. 

Water,    16  parts. 

B.  —  Pulverized  Alum,   1  part. 

Hot  Water,   4  parts. 


.    .  (40). 


When  a  perfect  solution  has  been  effected,  they  are  mixed,  well 
shaken,  and,  after  about  12  hours,  filtered.  The  prints,  having  been 
developed,  and  plunged  into  clean  water,  are  then  immersed  in  this 


46 


MODERN  HELIOGRAPHIC  PROCESSES. 


fixing  bath,  and  left  in  it  for  about  15  minutes;  then  they  are  put  in 
a  second  fixing  bath,  consisting  of 

Hyposulphite  of  Soda,  .    .    1  part.    )  v 
Water,  5  parts.  ) 

The  first  fixing  bath  (40)  may  be  used  several  times,  but  the  second 
one  (41)  must  be  renewed  for  each  batch  of  prints. 

After  this  double  fixing,  the  prints  are  washed  twice  in  water,  and 
then  hardened  in  a  solution  of 


Alum,  1  part. 

Hot  Water,  10  parts. 


(42). 


When  the  alum  is  perfectly  dissolved,  and  the  solution  cooled  and 
filtered,  the  prints  are  immersed  in  the  same  for  about  15  minutes. 

Finally,  the  prints  are  washed  in  pure  water,  and  kept  in  the  same 
for  from  3  to  4  hours.  The  water  must  be  renewed  every  half  hour. 
Then  the  prints  are  ready  to  be  hung  up  to  dry. 

Eastman's  Directions  for  Developing  and  Fixing  Prints  on  His 
Permanent  Bromide  Paper. 

Solution  No.  1. 

Oxalate  of  Potash,  ...    1  pound.  \ 

Hot  Water,  48  ounces.  (     .    .    .  (43). 

Acetic  Acid,  3  drams.  ) 


Solution  No.  2. 

Proto-Sulphate  of  Iron,  .    1  pound.  \ 

Hot  Water,  32  ounces,  i    .    .    .  (44). 

Acetic  Acid,  -J  dram.  ) 

(Or,  Citric  Acid,  .    .    .    .    i  ounce.) 

Solution  No.  3. 

Bromide  of  Potassium,  .  1  ounce.  ) 
Water,  1  quart.  ) 

These  solutions  must  be  kept  separate,  and  only  mixed  immediately 
before  using. 

To  Develop. — Take,  in  a  suitable  tray, 

Solution  No.  1,  .  . 
Solution  No.  2,  .  . 
Solution  No.  3,  .  . 


6  ounces.  ) 

1  ounce.  >  .  .  .  (46). 
-|  dram.  ) 


BROMIDE  OF  SILVER  EMULSION  PROCESS. 


47 


Mix  in  the  order  given;  use  cold.  After  exposure,  soak  the  paper 
in  water  until  limp;  then  immerse  in  the  developer. 

The  image  should  appear  slowly,  and  should  develop  strong,  clear 
and  brilliant.  When  the  shadows  are  sufficiently  black,  pour  off  the 
developer  and  flood  the  print  with  the 

Clearing  Solution: 

Acetic  Acid,  1  dram.  ) 

Water,  32  ounces.  ) 

Do  not  wash  the  print  after  pouring  off  the  developer  and  before 
applying  the  clearing  solution.  Use  a  quantity  sufficient  to  flow  over 
the  print — say  1  ounce  for  every  40  square  inches.  Allow  it  to  set  for 
1  minute,  then  pour  it  off,  and  apply  a  fresh  portion;  repeat  the 
operation  a  third  time,  then  rinse  in  pure  water,  and  immerse  for  10 
minutes  in  the 

Fixing  Bath : 

Hyposulphite  of  Soda,  .    3  ounces.  )  /ig\ 
Water,  16  ounces.  ) 

After  fixing,  wash  thoroughly  2  hours,  and  hang  up  to  dry.  Use 
fresh  developer  for  each  batch  of  prints.  With  a  glass-bottomed  tray, 
7  ounces  of  developer  are  sufficient  for  a  25  X  30  print. 

With  Eastman's  Permanent  Bromide  Paper,  no  toning  is  required; 
the  final  tones  are  obtained  entirely  by  development,  and  range  from 
a  soft  gray  to  a  rich,  velvety  black,  depending  somewhat  upon  the 
density  of  the  negative  and  the  quality  of  light  used  in  printing. 

Mr.  Eastman  recommends,  further,  to  keep  the  dishes  and  hands 
clean,  and  never  to  use  a  tray  that  has  been  used  for  developing 
with  oxalate  for  anything  else. 

Preparation  of  the  Gelatine  Emulsion. — The  following  emulsion 
does  not  give  to  paper  the  highest  degree  of  sensitiveness,  but  one  of 
fair  rapidity. 

1st.  Let  the  following  4  solutions  be  prepared,  each  in  a  separate 
jam-pot : 


A. — Bromide  of  Potassium,  .  .  4  drams  52  grains.  > 
Nelson's  No.  1  Gelatine,  .  1  dram  8  grains. 
Distilled  Water,   ....  5  ounces  1  dram. 
Hydrochloric  Acid  Solu- 
tion (1  per  cent.)    .    .  3  drams. 


(49.) 


B. — Nitrate  of  Silver,   343  grains.  )  z^qx 

Distilled  Water,   7  ounces.) 


48 


MODERN  HELIOGRAPHIC  PROCESSES. 


C. — Iodide  of  Potassium, 
Distilled  Water, 


30  grains. 
If  ounces, 


■  j     ...  (51). 


D. — Hard  Gelatine,  ....    6  drams  52  grains.  )  ,-o\ 
Distilled  Water,     ...    8  ounces.  ) 

2d.  Let  A  and  D  stand  till  the  gelatine  is  thoroughly  soaked,  as 
indicated  by  its  being  quite  soft.  Then  let  all  the  water,  not  absorbed 
by  the  gelatine,  be  poured  off  of  D,  and  as  much  water  as  possible 
squeezed  out  of  the  gelatine. 

3d.  Place  the  pots  containing  A  and  B  in  hot  water,  till  the  solu- 
tions are  at  about  120°  Fahrenheit;  then  pour  A  into  a  large  bottle. 

From  this  time,  all  operations  must  be  performed  in  the  most  feeble  ruby 
light  possible. 

4th.  Now  add  a  little  of  B  to  the  gelatine  solution  already  in  the 
large  bottle,  and  shake  well.  Small  additions  of  B  are  made,  so  that 
it  is  poured,  in  10  to  12  stages,  into  A,  the  whole  being  well  shaken 
after  each  addition,  and  a  very  thorough  agitation  being  given  at 
the  end. 

5th.  Add  0  to  the  emulsion  in  the  bottle,  and  shake  again. 

6th.  Pour  the  whole  emulsion  into  a  glass  jam-pot,  and  place  it  in 
a  deep  saucepan,  or  similar  vessel,  containing  hot  water.  A  loose  lid 
should  cover  the  jam-pot,  to  prevent  condensed  water  from  dropping 
off  the  lid  of  the  saucepan  into  the  emulsion.  Then  put  the  lid  on 
the  saucepan,  and  bring  the  water,  as  rapidly  as  possible,  to  a  boil, 
and  let  the  emulsion  remain  for  30  minutes  in  the  boiling  water. 

If,  before  heating  the  emulsion,  a  drop  of  the  same  be  placed  on  a 
glass  plate,  it  will  look  red  by  transmitted  light.  After  boiling  the 
emulsion,  such  a  drop  will  be  a  more  or  less  near  approach  to  blue 
in  color. 

7th.  Take  off  the  lids  of  the  saucepan  and  jam-pot,  add  the  soaked 
gelatine,  D,  and  stir  the  compound  well,  to  mix  it.  Then  place  the 
pot  with  the  emulsion  in  a  cool,  dark  place,  and  allow  it  to  set,  which 
requires,  in  a  moderately  cool  place,  a  couple  of  hours. 

This  is  the  best  time  to  interrupt  the  process,  if  required  to  do  so, 
as  the  emulsion  may  be  left  in  this  state,  in  a  cool  and  perfectly  dark 
place,  for  a  few  days,  without  being  destroyed. 

8th.  Place  an  ordinary  hair-sieve  in  a  suitable  vessel  full  of  cold 
water,  put  a  lump  of  the  stiff  emulsion  in  a  piece  of  coarse  canvas, 
such  as  ladies  do  worsted  work  on,  place  under  water  in  the  sieve, 
and  twist  the  canvas  up,  so  as  to  cause  the  emulsion  to  pass  through, 
in  fine  shreds,  into  the  water  in  the  sieve.  .  Now  wash  the  divided 
emulsion  well  for  half  an  hour,  either  by  letting  water  run  into  the 
sieve,  or  by  frequently  changing  the  water  in  the  vessel. 


BROMIDE  OF  SILVER  EMULSION  PROCESS. 


49 


The  object  of  the  washing  process  is  to  remove  the  crystallizable 
nitrate  of  potash  —  one  of  the  products  of  decomposition  —  and  the 
soluble  bromide  from  the  emulsion.  The  bromide  and  iodide  of  silver, 
formed  in  preparing  the  emulsion,  and  which  cause  the  emulsion  to  be 
sensitive  to  light,  are  insoluble,  and  remain  in  the  emulsion. 

9th.  Remove  the  sieve,  with  the  emulsion,  from  the  washing  vessel, 
and  place  it  in  a  convenient  position,  so  that  the  superfluous  water 
may  drain  off.    This  requires  at  least  half  an  hour. 

10th.  Re-melt  the  emulsion,  filter  through  several  thicknesses  of  muslin, 
and  add  2-j-  ounces  of  methylated  alcohol.  The  emulsion  is  now  finished, 
and  ready  for  coating  the  paper.  One  fluid  ounce  of  emulsion  will 
cover  -J  to  J-  square  feet  of  paper.  The  coating  should  be  (before  dry 
and  set)  about  ^  to  inch  thick.  The  emulsion  may  be  kept  in  a 
bottle,  in  a  dark  place,  for  some  time. 

The  following  table  compares  the  proportions  of  ingredients  of  the 
emulsion  above  described,  with  a  few  other  formulae : 


Nitrate 

of 
Silver. 

Bromide 

of 
Potash. 

Bromide 
of 

Amnion. 

Iodide 

of 
Potash. 

Gelatine 
(Total).. 

Nitric 
Acid. 

Alcohol. 

Glycerine. 

Common 
Beer. 

Fair  Rapid,  .  . 

(343 

292 

30 

480 

o 

1200 

(365 

294 

480 

4 

1130 

1130 

Much  Used,  .  . 

480 

240 

480 

5760 

Slow  and  Sure, 

(360 

252 

252 

480 

2160 

(357^ 

239 

239 

52 

480 

4 

All  in  grains. 


Some  formulae  say  that  the  emulsion  must  not  be  boiled,  but  to 
apply  such  a  degree  of  heat  as  will  just  liquify  the  gelatine. 

In  order  to  increase  the  sensitiveness,  the  emulsification  is  allowed 
to  proceed  for  several  hours — even  for  days. 

Coating  the  Paper  with  the  Emulsion. — To  coat  paper  uniformly 
with  gelatine  emulsion,  by  hand,  is  somewhat  difficult.  The  following 
method,  which  Husnick  recommends,  seems  to  be  the  simplest : 

The  sheet  of  paper  is  first  plunged  into  warm  water  (about  100°  F.), 
then  a  glass  plate  —  of  the  same  size  as,  or  a  little  larger  than,  the  paper — 
is  slipped,  in  the  water,  under  the  paper,  and  with  it  the  paper  is 
lifted  out,  thus  causing  it  to  lie  flat  on  the  glass.  If  the  sheet  be 
large,  it  may  be  taken  out  of  the  water  with  the  hands,  and  laid  upon 
a  glass  plate,  or  a  well-varnished  board,  and  squeegeed  down.  The 
surplus  of  the  water  being  drained  from  the  paper,  the  glass  plate,  or 
the  board,  is  placed  upon  a  level  table  or  stand  (tripod  with  adjust- 
ing screws).    After  the  water  is  partly  evaporated,  the  paper  being  still 


50 


MODERN  HELIOGRAPHIC  PROCESSES. 


damp,  the  edges  of  the  paper  are  hent  up  all  around,  about  £  inch,  so 
as  to  form  a  shallow  pan;  then  sufficient  of  the  liquified  emulsion,  to 
about  half  cover  the  sheet,  is  poured  in  the  center  of  the  paper,  and 
the  glass  plate  or  board  tilted  in  all  directions,  in  order  to  spread  the 
emulsion  evenly.  A  strip  of  stiff  paper,  or  a  card,  may  be  used  to 
spread  it  over  places  not  covered.  Finally,  the  glass  plate,  or  board, 
with  the  coated  paper,  is  again  brought  into  an  accurately  level  position, 
and  the  emulsion  allowed  to  set;  then  the  paper  is  hung  up  to  dry. 
This  must  all  be  done  in  the  most  feeble  red  light. 

Some  authorities  recommend  to  use  a  glass  rod  for  distributing  the 
emulsion ;  others  to  float  the  dampened  paper  upon  the  emulsion,  which 
is  kept  liquid  in  a  water  bath,  and  then  to  place  the  paper  upon  a 
level  glass  plate,  marble  or  slate  slab. 

Manufacturers  of  emulsion  paper  have  machines  especially  con- 
structed for  the  purpose  of  coating  the  paper  in  rolls. 


X. 


PROCESSES  WITH  SALTS  OF  IRON. 

1.  Sensibility  op  Ferric  Salts  —  Properties  of  Ferric  and  Ferrous 
Salts  —  Early  Discoveries. 

One  of  the  first,  if  not  the  first,  records  we  have  of  photography 
undertaking  the  duties  of  a  copying  clerk,  is  that  by  Prof.  Alexander 
Herschel.  He  tells  us  how  his  father,  Sir  John  Herschel,  made  use  of 
heliography  with  ferric  salts — the  Cyanotype  or  Blue-print  Process — 
for  copying  his  calculations  and  intricate  tables.  Sir  John  Herschel 
discovered,  about  the  year  1840,  that  certain  of  the  persalts  of  iron — 
the  ferric  salts — when  exposed,  in  the  presence  of  organic  matter, 
undergo  decomposition,  and  are  reduced  to  the  state  of  proto-salts,  or 
ferrous  salts.  We  are  also  indebted  to  Poitevin  for  numerous  interest- 
ing developments  in  this  department. 

It  is  now  accepted,  that  all  ferric  salts,  in  the  presence  of  organic 
substances,  are  more  or  less  sensitive  to  light.  Dr.  Eder,  of  Vienna, 
has  determined  the  relative  sensitiveness  of  a  number  of  ferric  salts. 
He  found  that  a  watery  solution  of  equal  molecules  of  ferric  chloride 
and  oxalic  acid  was  the  quickest  to  be  decomposed  by  the  action  of 
white  daylight.  He  used  solutions  containing  f  per  cent,  of  iron,  and 
measured  the  photo-chemical  decomposition  by  the  quantity  of  ferrous 
salt  formed  in  the  same  time,  in  the  same  light,  and  at  the  same 
temperature  (70°  to  77°  F.).  The  results  of  Dr.  Eder's  investigation 
are  contained  in  the  following  table,  in  which  the  quantity  of  ferrous 
chloride  formed  in  a  certain  time,  in  a  solution  of  ferric  chloride  and 
oxalic  acid,  is  placed  equal  to  100 : 


1.  Ferric  Chloride  +  Oxalic  Acid,    ....  100. 

2.  Ferric  Oxalate,   89. 

3.  Ferric  Ammonium  Oxalate,   80. 

4.  Ferric  Tartrate,   80. 

5.  Ferric  Potassium  Oxalate,   78. 

6.  Ferric  Chloride  +  Tartaric  Acid,     ...  25. 

7.  Ferric  Chloride  +  Citric  Acid,     ....  19. 

8.  Ferric  Ammonium  Citrate,   15. 


The  figures  have  only  full  validity  for  solutions  containing  from  1 
to  5  per  cent,  of  the  ferric  salt.    With  an  increasing  density,  there  is, 

51 


52 


MODERN  HELIOGRAPHIC  PROCESSES. 


in  general,  an  increasing  sensitivity  of  the  solution,  and,  at  the  same 
time,  a  corresponding  decrease  in  the  quantity  of  ferrous  salt  formed 
in  the  various  solutions.  This  also  pertains  to  paper  saturated  with 
the  solutions  and  dried.  Dr.  Eder  exposed  to  light  strips  of  such 
paper  in  a  Vogel  photometer,  and  treated  them,  afterward,  with  a  solu- 
tion of  ferricyanide  of  potassium,  and  so  received  the  degrees  of  sensi- 
bility to  light  in  blue  color.  These  tests  proved,  also,  the  mixture 
of  ferric  chloride  and  oxalic  acid  to  be  the  most  sensitive  of  all.  Less 
sensitive  is  the  ferric  oxalate;  then  follows  the  ammonium  and  sodium 
ferric  oxalate,  and  still  less  decomposed  is  the  ferric  oxalate  of  potas- 
sium. The  difference  of  sensitiveness  between  the  double  salts  is  not 
so  great  as  with  the  solutions  —  especially  in  the  sodium  and  ammonium 
salts,  which  are  nearly  equally  sensitive  to  light. 

The  process,  which  goes  on  when  these  salts  are  exposed  to  the 
action  of  light,  consists  in  the  separation  of  carbon,  in  the  form  of 
carbonic  acid,  and  the  formation  of  the  corresponding  ferrous  salts. 
The  process  goes  on  the  most  regularly  with  the  oxalate,  as  thereby 
the  liberated  quantity  of  carbonic  acid  is  almost  equal  to  the  theoret- 
ical amount;  much  more  irregularly  with  the  citrate  and  tartrate, 
whereby — beside  carbonic  acid — acetic  acid,  oxalic  acid,  etc.,  are  formed. 

Ferricyanide  of  potassium  —  or  red  prussiate  of  potash  —  produces, 
with  a  ferrous  salt,  a  dark-blue  precipitate,  but  none  with  a  ferric  salt. 

Ferrocyanide  of  potassium  —  or  yellow  prussiate  of  potash — produces, 
with  a  ferric  salt,  a  dark-blue  precipitate;  with  a  ferrous  salt,  it  pro- 
duces a  white  or  light-blue  precipitate,  which  only  gradually  becomes 
darker.  The  formation  of  the  latter  precipitate  is  retarded,  and  the 
action  limited  to  the  surface,  by  the  presence  of  gum  arabic.  Tannic, 
gallic,  and  pyrogallic  acid  produce,  with  the  peroxide  salts  of  iron,  and 
with  the  sesquichloride,  bluish-black  precipitates,  but  with  pure  ferrous 
salt,  and  with  the  protochloride,  they  will  not  form  a  precipitate 
at  once  —  not  until  these  substances  have  taken  up  some  oxygen  from 
the  air. 

Poitevin  has  discovered,  1st,  that  a  dried  coating  of  a  solution  of 
ferric  chloride  and  tartaric  acid  becomes  hydroscopic  by  the  influence 
of  light;  2d,  that  a  coating  of  gelatine,  treated  with  a  solution  of 
sesquichloride  of  iron  and  tartaric  acid,  becomes,  after  drying,  com- 
pletely insoluble,  even  in  boiling  water,  and  that  the  solubility  is 
restored  by  the  action  of  light. 

The  peroxyd  salts  of  iron  —  as  well  as  the  salts  of  the  other  heavy 
metals,  silver,  uranium,  etc.,  which  possess  the  property  of  being  com- 
pletely or  partially  reduced  by  light,  in  the  presence  of  organic  sub- 
stances— have,  in  this  condition,  also  the  ability  to  reduce  the  salts 
of  the  precious  metals,  silver,  gold,  and  platinum. 

Upon  the  sensitiveness  of  the  ferric  salts  to  light,  and  the  properties 
of  the  salts  of  iron  just  mentioned,  the  following  processes  are  based : 


IRON  PRINTS  EARLY  DISCOVERIES. 


53 


Herschel's  Processes,  Discovered  1840-1842. —  1st.  If  paper  be 
saturated  with  a  solution  of  ammonium  ferric  citrate,  and,  after  drying, 
be  exposed  to  the  action  of  light,  under  a  drawing,  or  the  like,  for  a 
sufficient  length  of  time,  a  negative  impression  will  result.  If  this 
negative  impression  be  thinly  coated  with  a  solution  of  ferrocyanide  of 
potassium  and  gum  arabic,  the  negative  will  disappear,  and,  in  its  place, 
a  positive,  of  blue  color,  will  gradually  make  its  appearance  on  a  green- 
ish-yellow ground.  This  picture  must  be  dried  quickly,  and,  if  the 
image  should  be  indistinct,  the  coating  with  the  ferrocyanide  must  be 
repeated.  In  strong  light  these  prints  will  fade ;  but  in  the  dark  their 
original  clearness  will  be  retained.* 

2d.  If  paper  be  prepared  with  a  solution  consisting  of  equal  parts 
of  ferric  citrate  of  ammonium  and  ferricyanide  of  potassium,  and  exposed 
to  the  light  under  a  drawing,  engraving,  etc.,  washed  in  water  and 
dried,  a  picture  will  be  obtained  having  white  lines  on  a  blue  surface  — 
that  is  to  say,  the  picture  will  be  a  negative  in  regard  to  light  and 
shade.  A  solution  of  mercurous  nitrate,  Hg2  (N0S)  2\2 H20y  will 
cause  the  picture  to  disappear.  If  the  paper  be  washed,  dried,  and 
smoothened  with  a  hot  flat-iron,  the  picture  will  again  be  developed,  but 
in  a  brown  color.  After  a  few  weeks,  the  picture  will  disappear  again, 
but  can  be  re-developed  by  renewed  ironing. 

3d.  If  paper  is  coated  with  a  solution  of  ferricyanide  of  potassium, 
and  exposed,  under  an  engraving,  to  the  direct  rays  of  sunlight,  for  an 
hour,  a  negative  picture,  in  white  lines  upon  a  blue  surface,  will  result, 
which  may  be  fixed  in  a  solution  of  sulphate  of  sodium  (Glauber's 
salt),  and  then  washing  it.f 

4th.  Chrysotype  Process. —  The  paper  is  floated  on  a  solution  of  ferric 
citrate  of  ammonium.  The  solution  must  have  such  a  strength,  that 
the  paper,  when  dry,  looks  yellow  —  not  brown.  After  exposure  to 
light,  the  print  is  floated  upon  a  diluted  and  neutral  solution  of 
chloride  of  gold.  This  developer  may  be  also  applied  by  means  of  a 
soft  brush.  The  image  appears  at  once,  in  a  purple  tone,  which 
gradually  becomes  darker  the  longer  it  is  exposed  to  the  solution. 
Thereafter  the  print  is  washed  in  water — which  must  be  renewed  several 
times  —  and  then  fixed  in  a  weak  solution  of  iodide  of  potassium,  washed 
again,  and  finally  dried.  From  a  positive  drawing,  a  negative  in  white 
lines  upon  a  purple  ground  will  be  obtained. 

Poitevin's  Direct  Process  (Ink  Pictures). —  The  process,  published 
in  1860  by  Poitevin,  and  by  means  of  which  positive  prints,  in  writing 
ink,  are  produced  from  a  drawing  or  engraving,  is  the  following :  Paper 
is  floated  on  a  solution  of 

*Atheneum,  1842-1845. 

tThe  exposure  must  last  much  longer  than  one  hour.— The  Author. 


54 


MODERN  HELIOGRAPHIC  PROCESSES. 


Ferric  Chloride,  ....    10  parts.  \ 

Tartaric  Acid,     ....      3  parts.  >     .    .    .  (53). 

Distilled  Water,  ....  100  parts.  ) 

Certain  French  papers,  sized  with  starch,  are  the  best  for  this  process. 
The  paper  should  be  left  in  contact  with  this  solution  but  a  short  time, 
and  must  be  dried  quickly,  by  moderate  heat.  The  paper,  so  prepared, 
has  a  lemon-yellow  color,  and  must  be  exposed,  under  a  positive  (tracing 
drawing,  etc.),  until  the  ground  appears  perfectly  white,  and  the  image, 
in  pale  yellow  lines,  is  visible.  In  order  to  make  the  appearance  of 
*»  the  picture  more  distinct,  a  little  sulphocyanide  of  ammonium  may  be 
added  to  the  sensitizing  solution.  This  addition  will  color  the  paper 
red,  and,  after  exposure,  a  red  picture  on  a  white  surface  will  be 
obtained.  After  the  print  has  been  taken  out  of  the  copying  frame,  it 
is  drawn  through  water  into  which  powdered  white  chalk  has  just  previ- 
ously been  stirred.  Then  it  is  plunged  into  a  solution  of  gallic,  tannic, 
or  pyrogallic  acid,  in  which  the  yellow  or  red  lines  of  the  image  will 
gradually  become  dark  bluish-black.  When  developed,  the  print  is 
washed  in  rain  water.  Hard  water  would  color  it  brown.  The  tint  of 
the  print  varies  according  to  the  developer  used.  Gallic  acid  will  pro- 
duce the  deepest  color.  The  bluish-black  picture  can  be  converted  into 
a  blue  one  by  washing  it  in  a  solution  of  ferricyanide  of  potassium,  to 
which  a  little  sulphuric  acid  has  been  added. 

Herschel's  Method  of  Converting  Iron  Prints  into  Iodide  op 
Starch  Pictures. —  The  paper  is  coated  with  a  solution  of  ferric 
chloride,  and  exposed,  under  a  positive  (for  example,  a  drawing),  until 
a  yellow  image  on  a  white  surface  is  visible.  Then  it  is  immersed  in 
a  solution  of  iodide  of  calcium  and  starch.  The  iodide  becomes  liberated, 
and  forms,  with  the  starch,  the  dark-blue  iodide  of  starch,  which  gives 
an  intense  shade  to  the  lines  which  were  pale  in  the  iron  picture. 

Halleur's,  Reynolds'  and  Phipson's  Processes. — About  the  same 
time,  and  independently  of  each  other,  Reynolds  and  Dr.  Phipson  dis- 
covered a  copying  process  with  ferric  oxalate  of  ammonium.  Phipson 
published  a  synopsis  of  his  process  in  October,  1861,  and,  soon  after 
this,  Reynolds  communicated  his  discovery,  as  a  novelty,  to  the  Chemical 
Society  of  Dublin.  Phipson  floated  the  paper  on  a  solution  of  ferric 
oxalate  of  ammonium  for  about  10  minutes,  exposed  the  same,  when 
dry,  under  a  negative,  and  developed  the  print  by  first  washing  it  in 
distilled  water,  and  then  plunging  it,  for  a  moment,  into  a  solution  of 
manganate  of  potassium,  to  which  a  few  drops  of  ammonia  had  been 
added.  In  this  bath,  the  originally  yellow  picture  quickly  turned 
brown.  He  then  washed  the  prints  again,  and  immersed  them,  for 
half  an  hour,  in  a  solution  of  pyrogallic  acid,  washed  another  time  in 


IRON  PRINTS  BLUE  PRINTS. 


55 


water,  and  then  dried  them.  The  prints  had  a  dark-brown  color. 
Reynolds  also  sensitized  the  paper  with  ferric  oxalate  of  ammonium, 
but  he  developed  the  prints  with  a  solution  of  nitrate  of  silver.  Both 
of  these  methods  seem  to  be  anticipated  by  D.  G.  E.  H.  Halleur,  who 
published,  in  1853,  in  his  book  on  "The  Art  of  Photography,"  the 
following  process  for  obtaining  negatives  from  positives,  and  vice-versa: 
Dissolve 


and  with  it  sensitize  the  paper.  When  dry,  the  paper  has  a  yellow 
color,  which  turns  brown  in  the  light.  The  faint  image  comes  out 
strongly  in  the  developer.  Ferricyanide  of  potassium,  nitrate  of  silver, 
ammonia,  or  chloride  of  gold  may  be  used  as  developers. 

If  potassium  ferricyanide  (red  prussiate  of  potash)  is  used  as  the 
developer,  it  should  not  be  too  much  diluted,  and  it  may  be  applied 
by  means  of  a  brush.  The  blue  picture  consists  of  Turnbull's  blue. 
The  prints  are  fixed  by  simply  washing  in  water. 

Nitrate  of  silver  solution  furnishes  dark  brown-black  pictures,  which 
are  also  fixed  by  plunging  them  into  water. 

Nitrate  of  silver  and  ammonium  produce  grayish-black  prints,  which 
are  also  to  be  fixed  in  water. 

Chloride  of  gold  gives  purple-colored  images,  which  turn  darker  in 
the  light. 

Halleur  mentions,  also,  that  paper,  prepared  with  ferric  ammonium 
oxalate,  or  citrate,  may  be  treated  with  a  solution  of  red  prussiate  of 
potash,  before  exposure  to  light. 

2.  Modern  Processes  by  which  Copies  in  White  Lines  upon  a  Blue 
Ground  are  Produced  from  a  Drawing  or  Tracing. 

All  the  preceding  methods,  and  several  others,  remained  almost  un- 
noticed, by  engineers,  architects,  or  draughtsmen,  for  a  number  of  years. 
Perhaps  the  reason  for  this  lay  in  the  fact  that  celebrated  authorities 
did  not  speak  very  highly  of  iron  pictures. 

Marion,  of  Paris,  was  the  first  who,  about  twelve  years  ago,  undertook 
to  manufacture  sensitized  "Blue  Print  Paper"  according  to  Herschel's 
discoveries.  The  imported  "Papier  Ferro  Prussiate,"  of  Marion,  was 
that  on  which  the  author  made  his  first  blue  prints.  The  attention  of 
American  scientific  and  technical  periodicals  was  attracted,  in  1878, 
to  this  method  of  copying  drawings,  writings,  etc.,  which  is  now  the 
most  extensively  used  heliographic  process.  It  is  especially  adapted 
for  large  working  drawings.  The  iron  salt  mostly  used  is  the  double 
salt  —  citrate  of  iron  and  ammonium. 


Ferric  Ammonium  Oxalate. 
Water,  


!  •  •  •  ^- 


56 


MODERN  HELIOGRAPHIC  PROCESSES. 


There  are  two  methods  in  use  for  producing  "  Blue  Prints "  with 
ferric  salts. 

In  the  one  method,  the  ferric  salt  and  the  ferricyanide  of  potassium 
are  applied  to  the  paper  in  one  solution,  while,  in  the  other,  the  papei 
is  coated  only  with  the  solution  of  a  ferric  salt,  and,  after  exposure  to 
light,  the  prints  are  developed  by  a  solution  of  the  ferricyanide.  Not 
all  ferric  salts  are  equally  suitable  for  either  method.  The  first  method  — 
in  which  the  salts  are  used  in  one  solution — is  the  simplest,  as  one  bath 
is  saved;  but  the  friends  of  the  other  method  claim  that  the  exposure 
required  is  five  or  six  times  as  long  as  that  needed  when  the  paper  is 
coated  with  the  ferric  salt  only.  The  formulae  for  the  sensitizing  solu- 
tion, given  by  different  authorities,  vary  more  or  less. 

Recipes  for  the  Sensitizing  Solution  for  Blue  Prints  without 
Development. —  The  following  is  one  of  Sir  John  HerscheVs  recipes,  in 
his  son's  (Prof.  Alexander  Herschel)  own  words.  (According  to  "Lon- 
don Photo  News.") 

"  The  solution  for  treating  the  copying  paper  is  as  under : 

"Citrate  of  Iron  (or  Ammonium  Citrate),  .  140  grains.  \ 

Ferricyanide  of  Potash,   120  grains.  >     .  (55). 

Dissolved  together  in  Water,  2  fluid  ounces.  ) 

"  The  solution  can  be  kept  in  a  glass-stoppered  bottle,  well  wrapped 
up  in  a  dark  cloth,  or  shut  up  in  a  dark  cupboard,  for  any  length  of 
time.  It  is  applied  to  the  paper  by  means  of  a  brush,  or  tuft  of  cotton- 
wool, and  the  surface  dried  in  the  dark.  Two  or  three  minutes'  bright 
sunshine  suffice,  if  the  original  is  on  thin  or  tracing  paper,  for  printing, 
and  the  fixing  is  done  by  washing  in  clear  water  for  a  few  minutes." 

The  following  formula  is  used,  in  the  laboratory  at  Willett's  Point,  with 
most  excellent  results.    (According  to  Jas.  S.  Pettit.) 


Solution  No.  1. 


Double  Citrate  of  Iron  and  Ammonia, 
Water,  


1  ounce. 
4  ounces 


A 


(56). 


Solution  No.  2. 


Red  Prussiate  of  Potassium, 
Water,  


1  ounce. 
4  ounces, 


:..! 


(57). 


For  use,  mix  equal  quantities,  and  float  paper  for  2  minutes. 


Captain  G.  Pizzighelli  calls  this  process  "  Negative  Cyanotype  Process," 
and  gives  the  following  instructions  :    Well  glue-sized  paper  is  (by  means 


IRON  PRINTS  BLUE  PRINTS. 


57 


of  a  wide  brush,  or  a  mechanical  device)  quickly  coated  with  the 
following  solution : 

Ferric  Ammonium  Citrate,    .    .    10  parts.  \ 

Red  Prussiate  of  Potassium,     .     8  parts.  >    .    .  (58). 

Water,  100  parts.  ) 

"When  dry,  the  paper  has  a  greenish-yellow  color,  and  becomes  blue 
in  the  light,  except  at  those  places  which  are  protected  against  the 
light  by  the  opaque  lines  of  the  drawing. 

The  printing  must  be  continued  until  the  lines  also  commence  to 
darken,  and  partly  disappear ;  then  the  print  is  taken  out  of  the  copy- 
ing frame,  and  simply  washed  in  water,  which  must  be  continually 
renewed  until  it  is  no  longer  colored.  During  the  washing,  the  lines 
gradually  become  clear,  and  finally  appear  —  pure  white  upon  the  blue 
surface. 

If  it  is  desired  to  give  more  brilliancy  to  the  picture,  it  is  only 
necessary  to  lay  the  same,  after  washing,  in  water  which  is  acidified 
with  5  per  cent,  of  hydrochloric  acid,  and  to  again  wash  the  print 
thoroughly. 

Haugh  and  Liesegang  give  the  following  two  formulae  for  the  sensi- 
tizing solution : 

Water,  80  parts.  \ 

Red  Prussiate  of  Potash,  ...     6  parts.  >    .    .  (59). 
Citrate  of  Iron  and  Ammonium,      5  parts.  ) 

The  solution  must  be  preserved  in  the  dark. 
Make  the  following  two  stock  solutions  : 


A. — Red  Prussiate  of  Potash,  ...      3  parts. 
Water,  25  parts. 


(60). 


B. — Ferric  Citrate  of  Ammonium,   .      1  part.  ) 

Water,   6  parts.  )    '    '    (  }' 

For  use,  mix  equal  volumes  of  A  and  B. 

Captain  Pizzighelli  and  Arthur  Baron  Huebl  use  paper,  sensitized  with 
the  following  solution,  in  the  photometer : 

Stock  Solution  A. 

Ferricyanide  of  Potassium,    .    .      8  parts.  )  ,R9v 
Water,     .    .  50  parts.  S    "    '  * 


58 


MODERN  HELIOGRAPHIC  PROCESSES. 


Stock  Solution  B. 

Ammonium  Ferric  Citrate,    .    .    10  parts.  )  ,fio\ 
Water,  5  parts.  S 

The  sensitizing  solution  is  prepared  shortly  before  use,  and  consists 
of  1  volume  of  solution  A  and  4  volumes  of  solution  B. 

Note. —  A  photometer  serves  to  judge  the  correct  time  of  exposure. 
It  is  simply  a  small  printing  frame  —  narrow,  and  long  in  proportion — 
made  so  as  to  open  easily,  like  a  book,  and  provided  with  means  for 
holding  the  sensitive  paper,  and  to  prevent  it  from  changing  its  posi- 
tion, while  the  frame  is  being  opened.  The  inside  of  the  glass  plate 
of  this  instrument  is  covered  with  tracing  paper,  in  such  a  manner 
that  there  are  squares  or  rectangles  covered  with  1,  2,  3,  4,  etc.,  thick- 
nesses of  paper.  On  that  strip  of  tracing  paper  which  is  in  contact 
with  the  sensitive  paper  numbers  are  printed  or  written,  in  opaque 
ink,  corresponding  with  the  number  of  thicknesses.  When  a  strip  of 
paper,  coated  with  the  above  solution,  is  exposed  to  light,  in  the 
instrument,  one  number  after  the  other  will  become  visible,  in  yellow 
lines,  upon  a  blue  or  light-green  surface.  When  the  number — which 
must  be  just  plainly  visible  —  for  a  certain  kind  of  print  has  been 
determined  and  noted,  by  a  few  experiments,  the  correct  time  of 
exposure  may  be  judged  at,  with  certainty,  in  all  future  cases. 

The  author  uses,  for  his  Blue  Prints,  a  stock  solution  composed  of 


Red  Prussiate  of  Potash,  ...  5  ounces  avoirdupois. 
Water,  32  fluid  ounces. 


(64). 


After  the  red  prussiate  of  potash  has  been  dissolved  —  which  requires 
from  1  to  2  days  —  the  liquid  is  filtered.  This  solution  remains  in  a 
good  condition  for  a  long  time.  Whenever  it  is  required  to  sensitize 
paper,  dissolve,  for  every  240  square  feet  of  paper, 

Citrate  of  Iron  and  Ammonium,  .  1  ounce  avoirdupois.  )  (65) 
Water,  .    .    4£  fluid  ounces.  ) 

and  mix  this  with  an  equal  volume  of  the  red  prussiate  stock  solution. 

The  reason  for  making  a  stock  solution  of  the  red  prussiate  of  pot- 
ash is,  that  it  takes  a  considerable  time  to  dissolve,  and  because  it 
must  be  filtered.  There  are  many  impurities  in  this  chemical,  which 
can  be  removed  by  filtering.  Without  filtering,  the  solution  will  not 
look  clear.  The  author  makes  no  stock  solution  of  the  ferric  citrate 
of  ammonium,  because  such  a  solution  soon  becomes  moldy  and  unfit 
for  use.    This  ferric  salt  is  brought  into  the  market  in  a  very  pure 


IRON  PRINTS  BLUE  PRINTS. 


59 


state,  and  does  not  need  to  be  filtered  after  being  dissolved.  It  dis- 
solves very  rapidly.  In  the  solid  form,  it  may  be  preserved  for  an 
unlimited  time,  if  kept  in  a  well-stoppered  bottle,  and  protected  against 
the  moisture  of  the  atmosphere.  A  solution  of  this  salt,  or  a  mixture 
of  it  with  the  solution  of  red  prussiate  of  potash,  will  remain  in  a 
serviceable  condition  for  a  number  of  days;  but  it  will  spoil,  sooner 
or  later,  according  to  atmospheric  conditions. 

The  greater  part  of  what  has  been  said  before,  about  sensitizing 
and  printing  in  general,  also  has  reference  to  blueprints.  (See  pages 
8,  9,  and  23  to  26.)  If  the  sensitizing  is  to  be  done  by  hand,  the 
author  prefers  to  apply  the  solution  by  means  of  a  sponge,  as  described 
on  page  8. 

If  pure  chemicals  and  suitable  paper  are  used,  and  the  paper  is 
quickly  dried  in  moderate  heat,  and  kept  tightly  rolled,  or  pressed  be- 
tween boards,  protected  from  light  and  moisture,  it  will  remain  in  a 
good  condition  for  a  long  time.  After  the  paper  has  been  sensitized, 
it  should  not  be  put  in  a  drawer  while  still  damp,  because  the  air  in  the 
drawer  would  become  moist,  and  the  paper  would  then  dry  too  slowly 
and  be  spoiled,  as  the  sensitizing  chemicals  would  soak  too  deeply  into 
the  fibres  of  the  paper,  and  it  would  be  impossible  to  receive  pure  white 
lines.  The  paper  should  be  hung  up  to  dry  in  a  warm  and  dark 
room,  and  never  be  stored  away  in  a  close  space  before  perfectly  dry. 
The  best  prints,  however,  will  be  obtained  when  freshly  sensitized  paper 
is  used. 

Four  ounces  of  sensitizing  solution,  for  blue  prints,  are  amply  suf- 
ficient for  coating  100  square  feet  of  paper,  and  cost  about  6  cents. 

In  washing  the  prints,  after  they  are  taken  out  of  the  printing  frame, 
the  instructions  given  by  Pizzighelli  must  be  strictly  observed.  If  the 
prints  are  only  soaked  in  a  small  quantity  of  water,  the  water  will  be 
colored  and  become  a  dyeing  liquid,  and  not  only  will  the  lines  not  turn 
out  perfectly  white,  but  the  backs  of  the  prints  will  also  become  tinted. 


Dr.  Vogel  sensitizes  the  paper  with  a  mixture  of  the  following  two 
solutions : 

A.  — Red  Prussiate  of  Potash,  ...    10  parts.  )  ,nn\ 

Water,  100  parts,  i  '    '  * 

B.  — Ferric  Oxalate  of  Potassium,    .    10  parts.  )  /fi7x 

Water,  100  parts,  i    '  ' 

The  two  solutions  are  mixed,  in  the  dark,  and  the  paper  coated, 
with  the  mixture,  by  means  of  a  sponge. 

The  exposure  and  fixing  in  water  is  done  in  the  same  way  as 
usual  with  blue  prints. 


60 


MODERN  HELIOGRAPHIC  PROCESSES. 


A  French  sensitizing  solution  consists,  according  to  "La  Nature,"  of 

Ferric  Tartrate  of  Potash,     .    .    15  parts.  \ 

Red  Prussiate  of  Potash,  ...    12  parts.  >    .    .  (68). 

Rain  Water,   250  parts.  ) 

Recipes  for  the  Sensitizing  Solution  for  Blue  Prints  with 
Development. — Poitevirts  sensitizing  solution  consists  of 

Ferric  Chloride,  10  parts.  ) 

Tartaric  Acid,  3  parts.  >    .    .  (69). 

Water,  100  parts.  ) 

The  paper  is  coated,  as  thinly  and  uniformly  as  possible,  with  this 
solution,  and  dried  in  a  moderate  heat.  The  prints  are  developed  with 
a  weak  solution  of  red  prussiate  of  potash. 

Carey  Lea's  Method,  according  to  " Silver  Sunbeam." — The  sensitizing 
solution  is  composed  of 

Double  Oxalate  of  Iron  and  Ammonium,  .  .  1  ounce.  )  ,^qn 
Rain  Water,  5  ounces.  )  * 

Prepare  and  filter  this  solution  in  a  dark  room.  Float  the  paper 
on  it  for  a  minute  or  more,  and  then  hang  it  up  to  dry.  So  prepared, 
the  paper  has  a  pale-yellow  color.  As  long  as  it  is  secluded  entirely 
from  light,  it  may  be  preserved  for  an  indefinite  time.  If  exposed, 
under  a  tracing,  or  negative,  to  the  direct  rays  of  the  sun,  3  to  4 
minutes  will  be  sufficient.  A  faint  image  is  produced  upon  the  paper; 
for  where  the  light  has  acted,  the  yellow  color  has  become  bleached 
or  decolorized. 

The  print  must  be  developed  immediately,  otherwise  the  actinic  im- 
pression becomes  annihilated.    The  developer  consists  of 

Ferricyanide  of  Potassium,     .    20  grains.  \ 

Oxalic  Acid,  20  grains.   >    .    .  (71). 

Water,  from  12-15  ounces.  ) 

The  prints  are  immersed  in  this  solution  for  2  or  3  minutes.  The 
image  starts  out  with  great  rapidity,  and  is  of  a  blue  color.  No  further 
fixing  is  required  than  that  of  washing  in  water  for  about  10  minutes. 
Too  much  washing  is  injurious. 

Carey  Lea's  Formulae,  according  to  Haugh  or  Liesegang. —  Formula  for 
the  sensitizing  solution : 

Oxalate  of  Iron  and  Ammonium,    ....    8-10  parts.  \ 

Oxalic  Acid,  -J  part,    i    .    .  (72). 

Water,   500  parts.  ) 


IRON  PRINTS  RED  PRUSSIATE  OF  POTASH  PRINTS. 


61 


The  paper  is  floated,  for  1  minute,  on  this  solution,  and  then  dried. 
The  exposure  requires,  in  the  sun,  from  2  to  3  minutes;  in  diffused 
light,  i  hour.  The  picture  is  developed  by  immersing  the  print  in  a 
weak  solution  of  red  prussiate  of  potash. 

The  addition  of  the  oxalic  acid  to  the  sensitizing  bath  causes  the 
white  parts  to  come  out  perfectly  clear. 

Dr.  Vogel  gives,  for  iron  prints  with  development,  the  following  recipe 
for  the  sensitizing  solution : 

Potassium  Ferric  Oxalate,    .    .    10  parts.  )  ,^o\ 
Water,  100  parts.  )    '    '    V.  " 

The  developer  for  blue  prints  consists  of 

Ferricyanide  of  Potassium,   .    .    10  parts.  ) 

Water,  .   .    .    .  '  100  parts.  )    '    '  * 

Developer  for  sepia-colored  prints  : 


Nitrate  of  Silver,  1  part. 

Water,  100  parts. 


(75). 


Red  Prussiate  of  Potash  Prints. —  Drawings,  etc.,  may  be  repro- 
duced, by  the  action  of  light,  on  paper  which  is  only  coated  with  a 
solution  of 

Ferricyanide  of  Potassium,  .    .      1£  parts.  )  ,7px 
Water,    .  100    parts.  )    '    '  * 

According  to  Herschel,  these  prints  must  be  fixed,  after  having  been 
taken  out  of  the  printing  frame,  in  a  solution  of  sulphate  of  soda. 
The  author  formerly  used,  for  this  purpose,  a  solution  of 

Sulphate  of  Soda  (Glauber's  Salt),  1  part.  ) 

Water,   .  24  parts.  )    '    '  { 

but,  after  having  made  a  large  number  of  these  prints,  he  found  that 
washing  in  water  is  sufficient  to  fix  them. 

The  greatest  objection  to  red  prussiate  prints  is,  that  they  require 
a  very  long  exposure  to  light. 

Niepce  prepared  the  paper  with  a  solution  of 

Ferricyanide  of  Potash,  ...  1  part.  ) 
Water,  5  parts.  ; 

He  exposed  until  the  prints  became  light-blue,  then  took  them 
out  of  the  printing  frame  and  developed  with  a  saturated  solution  of 


62 


MODERN  HELIOGRAPHIC  PROCESSES. 


bichloride  of  mercury  (corrosive  sublimate),  washed  them  in  water,  and 
poured  over  them  a  solution  of  oxalic  acid,  which  had  been  heated 
to  120°  to  130°  F. 

The  oxalic  acid  solution,  as  well  as  the  sublimate  solution,  was 
saturated  cold. 

After  washing  3  or  4  times,  the  prints  were  dried. 

On  account  of  the  extreme  virulence  of  the  bichloride  of  mercury, 
as  a  poison,  these  prints  have  no  practical  value  whatever. 

Toning  Blue  Prints. —  Converting  blue  prints  into  dark  blue-black  or 
dark-violet  prints. 

When  blue  prints  are  treated  with  a  solution  of 

Potassa  Hydrate  (Caustic  Potassa),  1  part.  ) 

Water,   300  parts. )    '    '    1  '* 

the  blue  color  (Prussian  blue)  will  be  decomposed,  and  a  rusty,  yellow- 
ish-brown substance  —  ferric  hydrate — will  be  left  on  the  paper.  If, 
then,  a  solution  consisting  of 

90  per  cent.  Alcohol,    ....    25  parts.  \ 

Water,  30  parts.  [    .    .  (80). 

Gallic  Acid,  4  parts.  ) 

be  poured  over  the  print,  the  rusty  color  —  the  peroxide  of  iron  —  will 
give  place  to  a  fine  violet-black,  which  is  identical  with  common  writing 
ink.    (According  to  Marion  and  Winkler.) 

Converting  Blue  Prints  into  Brown  Prints. — The  dried  blue  print 
is  immersed  in  a  solution  of 

Aqua  Ammonia,  containing  22  \ 

per  cent,  of  the  Am.  Gas,    .    1  part.    >    .    .  (81). 
Distilled  WTater,  9  parts.  ) 

and  left  in  the  same  until  the  blue  color  has  entirely  disappeared,  which 
will  take  from  2  to  4  minutes.  The  print  is  rinsed  in  clean  water,  and 
then  plunged  into  a  filtered  solution  of 

Tannic  Acid,  1  part.    )  s^) 

Distilled  Water,  50  parts.  ) 

and  kept  in  the  same  for  about  12  hours.  If,  after  this  time,  the  color 
of  the  print  be  not  as  dark  as  desired,  it  may  be  intensified  by  adding 
to  the  bath  a  few  drops  of  ammonia  water.  After  one  or  a  few 
minutes,  it  is  taken  out  of  the  solution  and  thoroughly  washed  in 


SILVER  NEGATIVE  BLUE  POSITIVE  PRINTS. 


63 


plenty  of  water.    The  prints,  having  changed  their  color  in  this  man- 
ner, are  very  beautiful,  and  resemble  sepia  drawings.    ("  Phila.  Photo.") 
A  greenish  tone  may  be  given  to  blue  prints  by  immersing  them, 
after  washing,  in  a  1  per  cent,  solution  of  sulphuric  acid. 


Silver  Negative  and  Blue  Positive  Prints. 

A  Patent  Process  of  Making  Photographic  Copies,  or  Fac-Similes  of  Draw- 
ings, etc.  Abridgment  of  U.  S.  Patent  No.  259,094,  of  June  6,  1882, 
to  Sager  Chadwick,  of  Philadelphia,  Pa. 

To  produce  this  copy,  or  fac-simile,  the  following  process  and  mix- 
ture of  ingredients  are  employed  :  First  clean  a  glass  plate  with  aqua- 
fortis and  wash  it.    Then  coat  it  with  the  following  solution : 


Gelatine,  120  grains.  \ 

Chrome-Alum,   30  grains.  > 

Water,  10  ounces.  ) 

When  dry,  flow  over  it  collodion  prepared  as  follows : 


.  (83). 


Alcohol,  

Ether,  

Gun  Cotton,     .    .  . 
Iodide  of  Potassium, 
Iodide  of  Cadmium, 
Bromide  of  Cadmium, 


10  ounces. 

10  ounces. 
100  grains. 

40  grains. 

60  grains. 
•  60  grains. 


(84). 


Then  immerse  the  plate  in  a  bath  of  the  following  solution : 


Distilled  Water,  .  .  . 
Nitrate  of  Silver  (CP.), 
Nitric  Acid  (C.  P.),    .  . 


10  ounces. 
1  ounce. 
1  drop. 


(85). 


After  an  immersion  of  about  5  minutes,  the  plate  is  taken  out  and 
drained;  then  placed  in  a  dark-slide,  and  exposed,  in  a  camera,  for 
about  3  minutes,  to  the  drawing  to  be  reproduced.  The  plate  is  then 
taken  to  a  dark  room,  and  flowed  with  the  following  solution  : 

Protosulphate  of  Iron,   |  ounce. 

Protosulphate  of  Iron  and  Ammonia,  ...  £  ounce. 

Acetic  Acid,   1  ounce. 

Water,   16  ounces. 


(86). 


When  the  image  has  been  developed,  the  plate  is  fixed  with  a  solution 
of  the  following  proportions  : 


Cyanide  of  Potassium, 
Water,  


1  ounce. 
8  ounces 


.1 


(87). 


64 


MODERN  HELIOGRAPHIC  PROCESSES. 


When  fixed,  the  plate  or  image  is  intensified  with  a  weak  solution 
of  sulphuret  of  potassa.  When  the  plate  has  become  dry,  it  is  ready 
to  print  from,  by  placing  back  of  it,  in  a  pressure  frame,  paper,  or 
other  support,  material  prepared  in  the  following  manner: 


or  other  equivalent  known  substitute,  soluble  in  water,  is  applied  to  the 
paper  by  means  of  a  sponge,  and  then  exposed  to  sunlight  for  from 
5  to  10  minutes.  When  printed,  the  material  is  placed  in  clean  water 
and  thoroughly  washed.  The  result  is  a  fac-simile  of  the  original,  with 
blue  lines  on  a  plain  ground. 

What  I  claim  as  my  invention  is : 

1.  The  process  hereinbefore  described  of  producing  fac-similes  in 
ferroprussiate  colors,  which  consists,  essentially,  in  combining  gum  arabic, 
or  an  equivalent  substitute,  with  the  ferroprussiate  sensitizing  solution, 
forming  the  lines  or  image  thereon  by  exposure  to  light,  and  then 
divesting  the  ground  or  field  of  soluble  and  surplus  prussiate  by  means 
of  water,  substantially  in  the  manner  and  for  the  purpose  set  forth. 

2.  The  sensitizing  solution,  consisting  of  gum  arabic,  or  an  equiva- 
lent substance,  mixed  with  ferroprussiate  of  potash,  and  ammonia  and 
iron  chemically  combined  with  a  vegetable  acid,  as  and  for  the  purpose 
set  forth. 

3.  Processes  by  Means  of  which  Positive  Copies,  in  Blue  Lines  Upon 
a  White  or  Light-Colored  Ground,  are  Produced  from  a 
Drawing  or  Tracing  —  Direct  or  Positive  Cyanotypes. 

The  principles  on  which  these  processes  are  based  have  been  men- 
tioned already  on  pages  52  and  53,  when  we  began  to  treat  of  iron  prints. 
We  have  also  stated  Herschel's  method  of  producing  prints,  in  blue 
lines,  from  an  original  in  black  lines.  Herschel  coated  the  faint  nega- 
tive iron  print  thinly,  with  yellow  prussiate  of  potash  mixed  with  gum 
arabic.  Later  investigators  discovered  that  it  is  more  practicable,  and 
that  better  prints  are  obtained,  when  the  gum  is  mixed  with  the  sensi- 
tizing solution. 

The  best  results  are  obtained,  by  these  processes,  from  originals 
made  on  very  thin  paper,  tracing  paper  or  tracing  cloth,  with  perfectly 
opaque  ink.  The  paper  for  these  prints  must  also  be  well  sized,  so 
that  the  sensitizing  solution  will  be  kept  on  the  surface  of  the  paper. 
Glue-sized  paper  is  preferable. 


Red  Prussiate  of  Potassium,  .  120  grains. 
Citrate  of  Iron  and  Ammonia,  140  grains. 

Water,  1  ounce. 

Gum  Arabic,  10  grains. 


(88). 


IRON  PRINTS  DIRECT  PROCESS  PELLET'S  PATENT. 


65 


Henri  Pellet's  Process,  According  to  U.  S.  Patent. 


Clarisse  Zoe  Joltrain,  of  Paris,  was  the  first  to  manufacture  Sensitized  Paper 
for  a  Direct  or  Positive  Cyanotype  Process  (under  the  name  u Papier 
Gommoferric"),  according  to  Pellet's  Patent,  No.  241,713,  dated  May 
17,  1881,  of  which  the  following  is  an  abridgment : 

The  sensitizing  liquor  can  be  prepared  in  a  number  of  ways.  The 
following  compositions,  which  can  be  used  singly  or  mixed,  and  in 
which  the  proportion  for  each  ingredient  can  be  varied  with  the  nature 
of  the  paper,  or  surface,  on  which  the  reproduction  is  to  be  effected, 
the  time  to  be  consumed,  and  the  rapidity  with  which  the  operations 
are  to  be  performed  in  the  reproduction,  the  intensity  of  the  impression 
to  be  obtained,  and  similar  conditions,  are  given  as  examples,  viz : 


First  Type. 

Perchloride  of  Iron,  at  45°  Baume,  .     8  cub.  centimeters 

=  130  minims. 

Oxalic  Acid,  6  grams 

=  93  grains  troy. 

Water  to  make  the  whole  amount  to  100  cub.  centimeters 

=  3  fluid  ounces  -f- 183  minims^ 


(89). 


Other  salts  of  iron  can  be  used  in  place  of  the  perchloride.  This  liquor 
can  be  used  alone,  or  with  thickening  substances  —  such  as  gelatine, 
isinglass,  gum,  dextrine,  glycerine,  and  other  gummy  or  mucilaginous 
materials.  These  can  also  be  added,  in  varying  proportions,  to  the 
liquors  hereinafter  indicated. 

Second  Type. 

Perchloride  of  Iron,  at  45°  Baume,  .    15  cub.  centimeters 

=  243  minims. 

Citrate  of  Soda  or  Potassa,    ...     8  grams 

=123  grains  troy. 

Water  to  bring  the  whole  to  .    .    .100  cub.  centimeters 

=  3  fluid  ounces +  183  minims,  j 


(90). 


Third  Type. 

Perchloride  of  Iron,  at  45°  Baume,  ...  10  per  cent. 
Water,  90  per  cent. 


(91). 


The  surface  of  the  article  or  object  on  which  the  reproduction  is  to  be 
effected  is  impregnated  with  the  liquid  selected,  and  immediately,  or 
after  desiccation,  is  passed  through  an  alkaline  bath,  peroxide  of  iron 


66 


MODERN  HELIOGRAPHIC  PROCESSES. 


(ferric  oxide)  being  deposited.  The  operation  of  sensitizing  is  com- 
pleted by  means  of  oxalic,  citric,  or  similar  acid,  or  corresponding 
salts,  with  or  without  gummy  or  mucilaginous  substances. 

Fourth  Type. 

Citrate  of  Iron,  or  Ammoniacal  Citrate  of  Iron,  \ 

3-5  grams  =  46 -77  grains  troy.  >    .    .  (92). 
Water  to  make  100  cub.  cent.  ==3  fluid  oz.-J-183  minims.  ) 

A  solution  of  citrate  of  iron  has  been  heretofore  used,  with  red  prus- 
siate  (ferricyanide  of  potassium),  to  obtain  white  lines  on  a  blue  ground. 
I  have  discovered  that,  by  omitting  the  red  cyanide  of  potassium  and 
adding  a  thickening  material,  this  new  liquor  would  give  the  results 
before  indicated. 

Fifth  Type. 

Perchloride  of  Iron,  at  45°  Baume,  .  6-8  cub.  centimeters 

=  97-130  minims. 
Tartaric,  Citric,  or  similar  Acid,     .  6-8  grams 

=  93-123  grains  troy. 

ammonia,  in  variable  quantities,  according  to  the  proportions  of  other 
materials ;  divers  thickening  or  gummy  materials  in  varying  proportions. 

The  sensitized  paper  is  prepared  by  hand,  or  by  a  machine,  with  a 
brush,  sponge,  or  other  suitable  agent.  Having  been  prepared  with  the 
liquor  of  any  of  the  types  before  mentioned,  it  is  exposed  to  light 
under  the  drawing,  bit  of  lace,  or  design  to  be  reproduced.  After 
exposure,  it  is  passed  through  a  bath  of  yellow  prussiate  (ferrocyanide 
of  potassium),  the  bath  being  concentrated,  or  dilute,  neutral,  slightly 
acid,  or  slightly  alkaline,  hot,  or  cold.  The  parts  corresponding  to  the 
black  portions  of  the  design,  or  pattern,  become  blue.  After  washing, 
the  paper  is  passed  through  a  discharging  bath  (dilute  acid  or  divers 
salts),  and  rubbed  on  its  upper  surface  or  not,  as  may  be  required. 

The  operation  can  be  modified.  For  example :  After  washing,  the 
paper  (without  passing  through  the  acid  bath)  can  be  simply  rubbed 
lightly  on  its  surface.  The  result  is  a  yellow  background.  The  paper 
can  also  be  passed  through  an  alkaline  bath  (lime,  sucrate  of  lime,  and 
other  salts  in  which  Prussian  blue  is  soluble),  and  then  through  acid, 
if  desired.  The  paper  used  can  be  blue,  colored,  silvered,  gilded,  and 
with  or  without  previous  designs.  To  the  sensitized  liquid  there  can 
be  added  soluble  or  insoluble  coloring  matter. 

The  liquors  and  methods  of  operation  already  indicated  can  be 
used  on  glass,  porcelain,  metals,  wood,  and  other  materials,  if  it  is 
desired,  to  obtain  photographic  negatives. 


IRON  PRINTS  DIRECT  PROCESSES  PELLET'S  PATENT.  67 

The  reproduced  lines  can  be  brought  out,  so  as  to  appear  blue- 
black,  by  the  application  of  two  or  more  successive  layers  of  a  liquor 
of  uniform  or  varying  density  for  the  two  layers. 

Two  layers  can  also  be  applied  in  various  other  ways :  first,  by 
using  the  acidulated  gum  and  then  the  perchloride;  second,  by  using 
the  perchloride  and  then  the  acidulated  gum ;  third,  by  using  the  gum 
alone  and  then  the  acidulated  perchloride;  fourth,  by  using  the  acidu- 
lated perchloride  and  then  the  gum. 

Blue-black  lines  can  also  be  obtained,  with  a  single  layer,  by  modi- 
fying the  proportions  of  the  salt  of  iron  and  the  organic  acid. 

The  liquor  which  is  commonly  employed  by  me  is  composed  of : 
first,  gum,  10  to  12  per  cent. ;  second,  salt  of  iron  (perchloride  at  45° 
Baume),  8  to  12  per  cent.;  third,  citric,  tartaric,  or  similar  acid,  1T\ 
to  3  per  cent. 

The  quantity  of  gum  can  be  increased  according  to  the  paper  used, 
and  to  the  atmospheric  conditions.  The  density  of  the  liquor,  and 
relative  proportions  of  the  gum,  salt  of  iron,  and  acid,  should  also  be 
modified  according  to  the  paper  employed,  the  sensitiveness  to  be 
obtained,  and  the  manner  of  treating  the  paper. 

Another  important  point  to  be  noticed  is,  that  the  density  should 
vary  with  the  temperature  or  humidity  of  the  air.  In  general,  the 
greater  the  heat  the  less  the  density  of  the  liquor. 

Instead  of  wholly  immersing  the  sheet  of  paper  in  the  bath  of 
prussiate — which  furnishes  a  more  or  less  blue  ground — the  sheet  may 
be  simply  floated  on  the  surface.  A  perfectly  white  ground  can  be 
thus  obtained,  and  less  prussiate  used.  The  time  required  for  develop- 
ment, by  the  prussiate,  varies  with  the  density  of  the  developing  liquid  — 
which  should  always  be  as  concentrated  as  possible  —  and  with  the 
accuracy  of  the  placing  of  the  paper. 

By  modifying  the  thickness  of  the  layer,  and  the  quantity  of  the 
iron  salt,  paper  can  be  obtained  of  great  sensitiveness;  and  this  can  be 
varied,  to  adapt  the  papers  to  different  countries  and  seasons,  and  to 
various  meteorological  conditions. 

As  soon  as  the  design  is  sufficiently  developed  by  the  prussiate,  the 
paper  is  passed  through  water,  and  a  bath  of  dilute  sulphuric,  hydro- 
chloric, or  other  suitable  acid  or  substance. 

The  gummy  matter  is  readily  detached  from  the  paper,  and,  after 
immersion  for  a  sufficient  time,  it  is  separated  by  a  jet  of  water,  all 
blue  parts  remaining  more  or  less  adherent.  The  design  then  appears 
of  a  blue-black  color.  A  solid  blue-black  impression  can  also  be  ob- 
tained by  drying  the  paper  after  passing  through  the  bath  of  prussiate. 
It  is  then  passed  through  the  water  and  the  acid. 

Ordinary  blue  impressions  can  be  deepened  to  blue-black  by  weak 
solutions  of  various  alkalies,  and  by  an  operation  of  washing,  which  is 
discontinued  at  the  proper  point.     Moreover,  blue-black  impressions 


68 


MODERN  HELIOGRAPHIC  PROCESSES. 


obtained  can  be  made  to  undergo  the  modifications  which  are  often 
effected  upon  Prussian  blue.  For  example,  by  treating  with  a  dilute 
solution  of  soda,  washing  well,  and  making  the  impression  black  with 
tannic  and  other  solutions. 

With  alkalies  alone — by  contact,  longer  or  shorter,  according  to  the 
strength  of  the  solution  —  a  variety  of  tints  can  be  produced.  In  the 
case  of  paper  improperly  treated,  with  too  little  or  too  much  liquor, 
it  suffices  to  pass  it  (by  machine  or  by  hand)  through  a  weak  liquor, 
or  pure  water,  to  restore  its  properties.  Thus  there  need  be  no  loss  of 
paper  in  the  manufacture. 

The  paper  can  be  sensitized  on  the  side  opposite  the  first  layer. 
For  particular  purposes,  both  surfaces  can  be  treated  by  one  operation, 
or  by  two,  so  as  to  form  designs  on  both  sides.  These  proofs  can  be 
bound  into  book  form. 

The  blue  or  black  can  be  strengthened  by  the  addition  of  a  few 
drops  of  chlorine  water,  nitric  acid,  or  other  similar  compound,  to  the 
acid  bath  or  washing  water. 

Papers  which  have  been  defectively  prepared,  can  be  restored  to 
their  original  condition  by  washing  with  a  roller,  or  by  hand,  in  water 
acidulated  with  hydrochloric,  sulphuric,  or  other  mineral  acid,  and  can, 
when  dry,  be  used  again. 

Having  thus  fully  explained  the  said  invention,  and  the  manner  of 
carrying  the  same  into  effect,  what  I  claim  is : 

1.  The'  method  of  producing  directly,  in  dark  or  colored  lines,  draw- 
ings, lace  patterns,  and  other  devices,  by  forming,  upon  the  surface  on 
which  the  reproduction  is  to  be  effected,  a  sensitized  layer,  containing 
a  salt  of  iron  —  as  ferric  salt  —  and  tartaric  or  other  organic  acid, 
afterward  exposing  the  said  layer  to  light,  under  the  pattern  or  device, 
and,  finally,  developing  the  parts  protected  by  the  opaque  or  semi- 
opaque  portions  of  the  pattern  or  device,  with  yellow  prussiate  of  pot- 
ash, which  forms  coloring  matter  by  combining  with  the  unaltered 
materials  of  the  sensitized  layer,  substantially  as  described. 

2.  The  method  of  reproducing  patterns  or  designs,  by  exposing  a 
surface  sensitized  with  a  layer  of  a  salt  of  iron  and  an  organic  acid, 
together  with  gummy  matter,  and  afterward  developing  the  protected 
parts  of  the  sensitized  layer  with  yellow  prussiate  of  potash,  or  other 
suitable  chemical  liquid,  substantially  as  described. 

3.  As  a  material  for  reproducing  designs  and  patterns  directly  in 
dark  lines  —  by  the  aid  of  transmitted  light,  and  of  a  bath  for  devel- 
oping the  protected  portions  of  the  sensitized  layer — paper,  paper-cloth, 
cloth,  or  like  fabric,  provided  with  a  sensitive  layer  of  gummy  matter, 
ferric  salt,  and  an  organic  acid,  substantially  as  described. 

4.  The  method  of  reproducing  patterns  or  designs,  by  exposing  to 
light,  under  a  pattern  of  the  character  indicated,  a  surface  sensitized 
with  a  salt  of  iron  —  as  ferric  salt  —  and  citric  or  oxalic  acid,  and 


POSITIVE   CYANOTYPE  PROCESS. 


69 


afterward  developing  the  sensitive  material,  upon  the  protected  parts,  by 
means  of  yellow  prussiate  of  potash,  or  other  chemical  liquid,  which 
produces  colored  lines  by  combining  with  the  said  sensitive  material, 
substantially  as  described. 

The  author  has  tried  Pellet's  process,  several  times,  with  the  liquids 
according  to  the  first  and  fourth  types,  and  with  liquor  commonly  em- 
ployed by  Pellet,  without  succeeding  in  producing  good  prints.  The 
background  was  always  more  or  less  colored. 

Captain  G.  Pizzighelli's  and  L.  v.  Itterheim's  Modification  of 
Herschel's  Positive  Cyanotype  Process. — The  following  three  stock 
solutions  are  to  be  prepared : 


A.  —  Gum  Arabic,   20  parts. 

Water,   100  parts. 

B.  —  Ferric  Ammonium  Citrate,  .    .  50  parts. 

Water,   100  parts. 

C.  —  Ferric  Chloride,   50  parts. 

Water,   100  parts. 


(94)  . 

(95)  . 

(96)  . 


Solution  A  will  become  sour  in  a  few  days,  and  then  be  unfit  for 
use;  B  and  C  will  remain  unchanged,  in  closed  vessels,  for  several 
weeks.    For  use,  mix 

A,  20  volumes.  \ 

B,  8  volumes,  i  .    .  (97). 

C,  5  volumes.  ) 

and  in  the  order  given,  as  otherwise  the  gum  will  coagulate.  The 
mixture  is,  at  first,  liquid,  but,  in  a  few  minutes,  will  become  viscid, 
and,  after  a  few  hours,  it  will  have  the  consistency  of  soft  butter.  In 
this  condition,  it  is  the  most  suitable  for  the  preparation  of  the  paper, 
and  maintains  its  usefulness,  for  several  days,  if  kept  in  the  dark  and 
in  a  closed  vessel. 

Well  glue-sized,  hard  drawing  paper  is  absolutely  necessary  for  this 
process.  Soft,  poorly  sized  paper  will  permit  the  sensitive  mixture  to 
soak  too  deeply  into  its  pores,  and  blue  spots  will  appear  in  the  prints. 

Pizzighelli  recommends  the  endless  drawing  paper,  known  as  the 
"  Imperial  Animal-Sized  Drawing  Paper."  The  author  has  used  "  Helios  " 
with  fair  results. 

In  order  to  sensitize  the  paper,  it  is  fastened  to  a  drawing  board  or 
table  by  means  of  thumb-tacks ;  then  the  mixture  is  applied,  by  means 
of  a  wide,  flat,  bristle  brush,  as  uniformly  and  quickly  as  possible,  but 
not  too  heavily.    As  soon  as  the  brush  begins  to  stick  to  the  paper, 


70 


MODERN  HELIOGRAPHIC  PROCESSES. 


the  surface  is  equalized  with  badger  softeners.  Some  operators  of  this 
process  use  a  velvet  brush  (a  small  board  covered  with  velvet)  for 
coating  the  paper  with  the  mixture,  whereby  the  equalization  of  the 
layer  with  the  softener  is  not  required. 

The  operation  of  coating  the  paper  may  be  performed  in  subdued 
daylight,  but  the  sensitized  paper  must  be  dried  quickly  in  a  dark  and 
warm  place.  It  must  be  preserved,  either  pressed  flat  or  rolled  with 
the  coated  surface  toward  the  outside — because  it  has  a  tendency  to 
curl  in  the  opposite  direction  —  and  protected  from  light  and  moisture. 

The  exposure  to  light  is  sufficient  when  the  yellow  picture,  upon  a 
dark-brown  surface,  is  plainly  visible,  which  will  require,  in  the  sun, 
from  3  to  10  minutes;  in  diffused  light,  15  minutes  or  more.  (The 
original  should  always  be  on  tracing  paper,  or  tracing  cloth,  for  this 
process.) 

In  order  to  develop  the  picture,  the  print  is  placed  upon  a  drawing 
board,  and,  by  means  of  a  soft  hair  brush  (of  otter's  or  camel's  hair), 
quickly — without  pressing  hard — coated  in  parallel  and  joining  strokeSj 
with  the  following  solution: 

Yellow  Prussiate,  20  parts.  ) 

Water,  100  parts,  i  *    *    {  }' 

The  image  will  appear,  in  a  few  seconds,  in  a  dark-blue  color.  If 
the  time  of  exposure  was  too  short,  blue  spots  will  also  appear  in 
places  where  they  should  not  be ;  sometimes  the  entire  sheet  will  become 
blue.  If  the  exposure  to  light  was  continued  too  long,  the  develop- 
ing of  the  blue  picture  will  proceed  very  slowly,  and  some  of  the  lines 
will  not  appear  at  all.  For  the  purpose  of  determining  the  correct 
time  of  exposure,  it  is  necessary  to  expose,  under  a  small  glass  plate 
and  tracing,  strips  of  the  same  prepared  paper,  at  the  same  time  and 
in  the  same  light,  alongside  of  the  printing  frame.  By  withdrawing 
one  of  the  strips,  from  time  to  time,  and  treating  it  with  the  yellow 
prussiate  solution,  the  exact  state  of  the  process  can  be  ascertained. 
During  the  time  that  the  strip  is  being  developed,  the  printing  frame  — 
and  the  glass  plate  which  serves  as  a  photometer  —  must  be  covered  or 
taken  into  subdued  light.  When  those  places  alone,  on  the  strips,  upon 
which  the  light  did  not  act,  and  no  other  parts,  become  blue,  the  print 
has  been  exposed  sufficiently  long,  and  must  be  taken  out  of  the  frame 
and  developed  in  the  manner  described.  Pizzighelli  gives  the  instruc- 
tion to  remove  the  yellow  prussiate  solution,  as  soon  as  all  the  details 
have  appeared,  quickly  and  without  delay,  by  means  of  a  strong  jet  of 
water  from  a  hydrant.  The  author,  however,  finds  that  this  can  easily 
be  overdone,  and  that  portions  of  the  blue  drawing  may  be  entirely 
removed  from  the  print  if  the  developer  was  not  allowed  to  act  for  n 
length  of  time  sufficient  for  the  formation  of  Prussian  blue,  not  only 


POSITIVE  CYANOTYPE  PROCESS. 


71 


on  the  surface,  but  through  the  entire  film,  to  the  paper.  This  time  is 
but  short,  and  the  deep  indigo-blue  lines  will  soon  begin  to  spread.  In 
all  cases,  a  blue  liquid  will  flow  all  over  the  sheet.  If  the  exposure  was 
continued  for  a  sufficient  length  of  time,  this  blue  liquid  will  not  spoil  the 
print,  and  the  coloration  which  it  produces  can  easily  be  distinguished 
from  the  blue  spots,  which  spring  up  and  continually  increase  in  num- 
ber and  size,  if  the  print  was  insufficiently  exposed  to  the  action  of  light. 
How  long  the  yellow  prussiate  solution  may  be  allowed  to  act  upon 
the  print,  before  the  lines  begin  to  spread,  will  soon  be  learned  from 
practice.  After  the  image  has  been  developed,  the  author  floats  the 
print,  back  upward,  for  a  few  minutes,  on  water,  until  the  lines  may 
be  recognized  from  the  back.  This  is  an  indication  that  the  developing 
process  has  continued,  in  the  lines  of  the  floating  sheet,  through  the 
film  and  into  the  superficial  pores  of  the  paper.  Then  the  print  is 
turned  over,  and  the  greenish-blue  film,  which  has  formed  on  the 
surface,  removed  by  means  of  a  soft  camel's  hair  brush.  When  this 
has  been  done  thoroughly,  the  print,  which  is  now  of  a  considerably 
lighter  blue  than  when  just  developed,  is  immersed  in  clean  water,  and 
allowed  to  remain  there  until  most  of  the  gum  film  has  dissolved.  If 
left  long  enough  in  the  water  bath,  this  film  will  entirely  dissolve,  the 
paper  will  have  a  uniform  light-yellow  tint,  and  the  blue  lines  of  the 
picture  will  become  somewhat  darker. 

Any  time  after  the  greenish-blue  film  has  been  removed  from  the 
print,  by  means  of  a  brush  or  a  jet  of  water,  the  print  is  immersed  in 
a  discharging  bath  of 

Hydrochloric  Acid,    ....    1  part.  j  /q^v 
Diluted  with  Water,  .    .    .    .10  parts.  )  '    '  * 

Pellet  recommends  to  substitute  sulphuric  acid  for  a  part  of  the 
hydrochloric  acid  (Bull  Soc.  Franc?.,  1880,  234),  in  order  to  diminish 
the  formation  of  muriatic  acid  vapors. 

Such  an  acid  bath  may  be  composed  of 

Water,  100  parts.  ) 

Hydrochloric  Acid,     ...       8  parts.  >  .    .  (100). 
Sulphuric  Acid,      ....       3  parts.  ) 

In  mixing,  the  acid  should  be  poured  into  the  water — not  vice- 
versa —  and  not  into  a  tray,  but  into  a  bottle  or  jug. 

In  the  acid  bath,  the  gum  film  scales  off  from  the  paper,  the  blue 
lines — which  faded  in  washing — again  become  darker,  and  a  blue 
picture,  on  pure  white  paper,  is  obtained. 

Finally,  the  prints  are  again  washed  in  water,  and  then  hung  up  to 
dry.     Some  operators  of  this  process  add  a  little  alum  to  the  last 


72 


MODERN  HELIOGRAPHIC  PROCESSES. 


rinsing  water,  in  order  to  restore  the  sizing  of  the  paper,  which  suffered 
a  little  in  the  previous  bath. 

Pizzighelli  immerses  the  print  in  the  acid  bath  as  soon  as  it  has 
been  washed  by  a  strong  jet  of  water  after  development.  But  if  the 
prints  are  first  soaked  in  water — as  we  recommend — the  major  portion 
of  the  gum  film  is  removed,  and  they  need  only  to  be  left  in  the  acid 
bath  a  few  minutes;  beside  which  this  bath  may  thus  be  used  for  a 
greater  number  of  sheets. 

The  following  interesting  notes,  concerning  this  process,  were  also 
originally  published  by  Pizzighelli:  The  positive  cyanotype  process  is 
especially  adapted  for  copying  tracings  executed  in  black  and  perfectly 
opaque  lines.  A  comparison  of  this  with  the  common  blue  print  process 
seems  to  be  superfluous,  and  a  comparison  with  the  new  heliographic 
methods — which  furnish  black  lines  on  a  white  surface — shows  that  the 
latter  processes,  in  general,  deserve  to  be  preferred,  but  that  the  gum 
and  ferric-salt  process  is,  by  all  means,  worthy  of  a  full  estimation,  on 
account  of  its  simplicity  and  rapidity. 

For  very  fine  drawings,  with  partly  gray  lines,  the  anthracotype 
process  is,  at  present,  indispensable,  especially  as  it  permits  versatile 
applications.  Itterheim's  nigrotypie  also  furnishes  excellent  results, 
but,  so  far,  only  in  the  hands  of  its  inventor. 

The  gum  and  ferric-salt  process,  on  the  other  hand,  may  be  prac- 
ticed, with  success,  by  persons  not  skilled  in  photographic  operations. 
The  preparation  of  the  paper,  the  printing,  and  the  development,  require 
but  little  time.    Therefore,  this  process  can  be  highly  recommended. 

The  addition  of  the  quantity  of  gum  arabic  above  given  is  absolutely 
necessary.  The  gum  not  only  acts  as  a  thickening  agent,  to  prevent 
the  solution  from  penetrating  the  paper,  but  it  also  possesses  the  prop- 
erty of  forming,  when  dry,  with  iron  salts,  a  substance  resembling  horn, 
which  does  not  easily  dissolve  in  water,  and  which  causes  the  developer 
to  act  only  superficially,  and  to  but  slowly  penetrate  the  film. 

Very  peculiar,  and  difficult  to  explain,  is  the  phenomenon  presented 
by  this  process — that  aqueous  developing  solutions  easily  penetrate  the 
parts  of  the  gum-iron  film  upon  which  the  light  did  not  act.  This 
peculiarity  exhibits  itself  in  the  fact  that  the  blue  image  —  consisting  of 
Prussian  blue  —  goes  through  the  film  to  the  surface  of  the  paper,  to 
which  it  adheres,  while  the  precipitate,  on  those  parts  which  were  ex- 
posed to  the  influence  of  the  rays  of  light,  is  only  formed  on  the 
surface  of  the  film.  More  striking  is  the  phenomenon  of  the  unexpected 
action  of  red  prussiate  of  potash  upon  the  film.  Any  one  who  is 
familiar  with  the  reaction  of  ferrous  salts,  would  expect  a  negative 
picture  (white  lines  upon  a  blue  surface) ;  but  this  is  not  obtained.  If 
a  solution  of  ferricyanide  of  potassium  is  used  for  developing,  a  positive 
blue  image  will  appear — just  as  with  the  yellow  prussiate,  but  somewhat 
slower  and  of  a  greenish  color — which,  in  the  hydrochloric  acid  bath, 


collache's  direct  blue  process. 


73 


also  becomes  blue  —  as  with  the  yellow  prussiate  of  potash  developer. 
It  is  supposed  that  this  abnormal  behaviour  of  the  ferric  gum  film  is 
due  to  the  fact  that  the  film  loses  its  penetrability  in  the  light. 

The  proportion  of  the  ferric  salts  may  be  changed,  from  those  given 
in  the  recipe,  without  affecting  the  chances  of  success.  In  general,  it 
may  be  said  that  a  larger  proportion  of  ferric  chloride  diminishes  the 
sensibility  to  light,  but  furnishes  pictures  of  darker  color. 

Ferric  ammonium  citrate  alone,  with  or  without  gum  arabic,  will 
give  no  good  results. 

The  quantity  of  gum  given  in  the  recipe,  has  proved  to  be  the 
best.  Less  gum  will  often  cause  blue  spots  in  the  paper;  a  larger 
amount  will  make  the  solution  so  thick  that  it  becomes  impossible  to 
coat  the  paper  uniformly  with  it. 

Gold  or  silver  solutions  have  no  developing  effect  on  paper  coated 
with  a  mixture  of  gum  arabic  and  ferric  salt  solutions. 

This  process  is  generally  credited  to  Pizzighelli  alone,  but  he  him- 
self states  that  he  has  worked  out  this  process  according  to  his  own 
experiments,  and  according  to  information  from  L.  v.  Itterheim,  who 
also  permitted  him  to  publish  his  communications. 

Collache's  Direct  Blue  Print  Process. —  Collache  received  a  patent, 
in  France,  in  the  year  1880,  on  the  following  process  : 

Sensitizing  Solution. 

Water,  1  fluid  ounce. 

Gum  Arabic,   32-46  grains  troy. 

Sesquichloride  of  Iron  Solution,  45°  Baume,  .  18-27  minims. 
Citric  Acid,   9-13^-  grains  troy. 


(101). 


The  solution  is  to  be  applied  to  the  paper  twice  by  means  of  a 
brush.    The  first  coating  must  be  dry  before  the  second  is  applied. 

Developing  and  acid  bath  is  the  same  as  in  the  Pizzighelli  process. 
The  prints  may  also  be  developed  with  nitrate  of  silver. 

This  sensitizing  mixture  has  the  consistency  of  dissolved  gum  arabic, 
and  can  be  applied  to  the  paper  easier  than  that  of  the  foregoing 
process.  The  prints  have  a  lighter  blue  color,  and  do  not  look  so 
brilliant  as  those  obtained  by  the  Pizzighelli  process. 

Joltrain's  Positive  Blue  Print  Process. — According  to  Liesegang. 

Sensitizing  Solution. 

Water,   1  fluid  ounce. 

Gum  Arabic,  114  grains  troy 

Ferric  Chloride  Solution,  at  45°  Baume,      .     48  minims.        ^  (102). 

Ferric  Sulphate,  23  grains  troy. 

Tartaric  Acid,   18  grains  troy. 


74 


MODERN  HELIOGRAPHIC  PROCESSES. 


The  author  uses  31  grains  troy  of  the  solid  sesquichloride  of  iron 
instead  of  48  minims  of  the  solution,  and  25  fluid  minims  of  ter- 
sulphate  of  iron  solution  (according  to  U.  S.  Pharmacopoeia)  in  place 
of  the  23  grains  of  the  solid  ferric  sulphate. 

The  developer  and  the  discharging  bath  are  the  same  as  in  the 
Pizzighelli  process. 

The  following  table  contains  the  proportion  of  the  ingredients  of 
the  sensitizing  solution  for  the  direct  blue  print  process,  according  to 
various  authorities : 


Developer  is 
Composed  of 

^Vater,  ounces. 

»o     «*,d     | .        •  • 

■a  w-8  • 

u  u 

Yellow  Pruss. 
of  Potash 
ounces. 

+a  -+3 

iH          r-i          rH        '-'oQ      t~iCC          •          7-1  ^ 

The  Sensitizing  Solution  is  Composed  of 

Common  Salt, 
grains  troy. 

!             .             .             '.           "*           rM  '. 

T-t  CO 

Tartaric  Acid, 
grains  troy. 

Citric  Acid, 
grains  troy. 

!      !      !     J"      !      !     X  ! 

Tersulphate  of 
Iron,  grains 
troy. 

.-I 

CM 

Sulphate  of 
Iron,  grains 
troy. 

Sesquichloride 
of  Iron,  grs. 
troy. 

^        ^  a 

CD           00             ,            00           rfl             |  — 1 
CO          <M          CM                       CO  CO 

oo  co 

CM  tH 

Citrate  of  Iron 
and  Am., 
grains  troy. 

CM           CM  l> 
lO         ^  cm 

Gum  Arabic, 
grains  troy. 

00  MS 
iO 

00                       O            |           O          VO            .  t>- 
iO           CD           CD            1            CM           lO             1  O 
00           tH  CM 
rt<  CO 

Water,  liquid 
ounces. 

Process. 

Pizzighelli,  accord, 
to  Liesegang,  .  . 

Pizzighelli,  accord, 
to  Spon,  

Pizzighelli,  acc.  to 
Lon.  Pho.  News, 

H.  Pellet,  accord,  to 

H.  Pellet,  accord,  to 
Photo  News,  .  .  . 

H.  Pellet,  accord,  to. 
Scientific  Am.,  of 
Oct.  25,  1884,  .  .  . 

Collache,  accord,  to 
Liesegang,  .... 

Joltrain,  accord,  to 
Liesegang,  .... 

poitevin's  process  —  colas'  formula. 


75 


Corrections  on  Blue  Prints. —  Blue  spots  on  positive  blue  prints 
may  be  removed,  and  corrections  on  negative  blue  prints  may  be  made, 
with  solutions  of  alkalies;  for  example,  with  lime  water — that  is,  the 
water  from  which  the  hydrate  of  lime  separates,  on  standing,  when 
quick  lime  is  slaked  in  water  —  or  with  a  solution  of 

Caustic  Potassa,     ....     1  part,    j  (103) 
Water,  25  parts.  ) 

These  alkaline  solutions  may  be  applied  by  means  of  a  small  brush, 
or  a  writing  or  drawing  pen. 

For  corrections  and  alterations  of  negative  blue  prints,  the  author, 
however,  prefers  white  writing  ink,  because  all  the  alkaline  solutions 
are  apt  to  spread  and  blot. 

4.  Processes  by  means  op  which  Positive  Copies,  in  Dark-Yiolet 
Lines  upon  a  White  or  Light-Colored  Surface,  are  Reproduced 
from  a  Tracing  in  Black  Lines  (Ink  Pictures). 

Poitevin's  Process. —  From  the  description  of  Poitevin's  ink-process, 
which  was  given  at  the  beginning  of  this  chapter,  it  will  be  seen  that 
Poitevin  uses  no  mucilaginous  substance  with  the  sensitizing  solution. 
This  is  the  reason  why  the  solution  penetrates  too  deeply  into  the 
paper,  and  sometimes  goes  entirely  through  it,  so  that  the  back  appears 
as  yellow  as  the  face.  This,  again,  causes  the  surface  of  the  finished 
prints  to  be  always  more  or  less  tinted.  Recent  operators  of  this  pro- 
cess mix  with  the  sensitizing  solution  gum  arabic  or  gelatine;  some 
operators  size  the  paper,  before  sensitizing,  with  a  1  to  30  arrow-root 
flour  solution.  But  even  with  gum  or  gelatine,  it  is  still  difficult  to 
always  obtain  a  perfectly  white  surface. 

Colas'  Formula. —  The  sensitizing  solution  consists  of 


Water,   30  parts. 

Gelatine,   1  part. 

Solution  of  Perchloride  of 

Iron,  at  45°  Baume,  .    .  3  parts. 

Tartaric  Acid,   1  part. 

Tersulphate  of  Iron,   ...  1  part. 


V  .    .  (104). 


A  solution  of  perchloride  of  iron,  at  45°  Baume,  has  a  specific 
gravity  of  1.45,  and  contains  50  per  cent,  of  sesquichloride  of  iron,  and 
50  per  cent,  of  water. 

The  developing  solution  is  composed  of 

W^ater,  50  parts.  ) 

Alcohol,  10  parts,  i    .    .  (105). 

Gallic  Acid,  1  part.  ) 


76  MODERN  HELIOGRAPHIC  PROCESSES. 

The  author,  finding  it  difficult  to  apply  the  sensitizing  solution  uni- 
formly, and  to  prevent  the  formation  of  an  infinite  number  of  small 
air-bubbles,  modified  this  recipe  as  follows : 


Water,   15  ounces 

Gum  Arabic,   1  ounce. 

Sesquichloride  of  Iron  (solid),     .  f  ounce. 

Tartaric  Acid,   -J  ounce. 

Monsel's  Salt  {2Fe20Z)  5S0Z),    .  %  ounce. 


The  Author's  Modification — Sensitizing  Solution. 

>  .    .  (106). 


This  solution  will  remain  in  good  condition  for  a  long  time.  It  is 
applied  to  the  paper,  by  means  of  a  soft  brush,  as  thinly  and  as  uni- 
formly as  possible.  It  is  best  to  use  the  prepared  paper  as  soon  as  it 
is  dry. 

The  exposure  to  light  must  be  continued  until  the  parts  of  the 
paper  affected  by  the  light  are  perfectly  white,  and  the  picture  is  visible 
in  yellow  lines. 

(This  refers  to  all  processes  under  this  head.) 


Gallic  Acid,  .    .  . 
Water,  80 


Developing  Solution. 

i  ounce  avoirdupois.  )  (-\m\ 
fluid  ounces.  S 


Or,  Gallic  Acid,   .     1  part.    )  M  08  ^ 

Water,   333  parts.  S    *    "  1 

This  solution  may  be  applied  by  means  of  a  camel's  hair  brush,  or 
the  print  may  be  immersed  in  the  solution.  As  soon  as  the  picture 
has  been  developed,  the  sheet  must  be  plunged  into  water  and  washed 
thoroughly.  The  lines  of  the  picture  consist  of  ordinary  writing  ink. 
It  is  not  necessary  to  develop  the  prints  as  soon  as  they  are  taken 
from  the  printing  frame. 

rThe  author  has  often  printed  during  the  light  part  of  the  day,  pre- 
served the  prints  in  a  dark  place,  and  developed  them  in  the  evening. 

The  prints  may  also  be  developed  as  positive  blue  prints.  For  this 
purpose  they  are  immersed  in  water,  wherein  the  gum  film  dissolves  a 
great  deal  sooner  in  those  places  which  were  affected  by  the  light  than 
in  those  on  which  the  light  did  not  act.  After  this,  the  prints  are 
developed  with  a  dilute  and  acidified  solution  of  red  prussiate  of  pot- 
ash, either  by  means  of  a  brush,  or  by  immersing  the  prints  in  this 
solution.  If  the  surface,  also,  of  the  paper  becomes  tinted  blue,  the 
print  was  either  not  long  enough  in  the  water  bath,  and  the  gum-iron 
film  not  entirely  removed,  or  the  exposure  was  not  sufficient.  When 
developed,  the  prints  are  washed  again,  in  order  to  remove  the  red 
prussiate  of  potash,  and  then  they  are  hung  up  to  dry. 


PROCESSES  WITH  SALTS  OF  IRON  CARBON  PRINTS.  7| 

A.  Fisch's  Method  of  Reproduction  of  Drawings  in  Black  Lin] 
upon  a  White  Surface.    (Ink  Pictures.)  —  Four  solutions  to  be  made : 

A.  — Gum  Arabic,  78  parts.  )  (109) 

Water,   850  parts.  S 

B.  —  Acetic  Acid,  78  parts.  )  (U0) 

Water,   336  parts.  ) 

C.  —  Ferric  Sulphate,     ....    48  parts,  j  (111) 

Water,  414  parts.  S 

D — Sesquichloride  of  Iron,  .    .  120  parts.  )  (112) 
Water,   .  120  parts.  ) 

Pour  C  into  J5,  add  A,  and  then,  while  constantly  stirring,  the  solu- 
tion of  sesquichloride  of  iron. 

With  this  mixture  the  paper  is  thinly  coated,  by  means  of  a  brush, 
and  quickly  dried  at  a  temperature  not  exceeding  100°  F. 

The  paper  will  remain  in  a  serviceable  condition  for  about  2  weeks. 
The  exposure,  under  tracing  paper,  requires,  in  the  sun,  from  10  to  12 
minutes.  The  unprotected  parts  of  the  paper  must  lose  their  yellow 
color  in  the  light.  When  the  ground  is  perfectly  white,  the  print  is 
floated  on  a  solution  of 

Gallic  Acid  or  Tannin,  .  31-46    parts.  \ 

Oxalic  Acid,     ....         1£  parts.  >    .    .  (113). 

Water,   1,700    parts.  ) 

without  wetting  the  back  of  the  prints.    Wash  well  and  dry. 


5.  Poitevin's  Direct  Positive  Carbon  Prints. 

Upon  Poitevin's  discovery,  that  a  mixture  of  gelatine,  ferric  chloride, 
tartaric  acid,  and  water,  becomes  insoluble  —  even  in  hot  water — on 
drying,  this  and  the  following  process  are  based : 

The  paper  is  first  coated  with  a  solution  of  gelatine,  colored  with 
fluid  Japan  drawing  ink.  One  part  of  gelatine  to  about  30  parts  of 
water  is  a  good  proportion.  The  best  way  of  coating  the  paper  is  to 
float  it  upon  the  hot  gelatine  solution.  The  so-called  carbon  or  pig- 
ment paper  (paper  coated  with  a  mixture  of  gelatine  and  a  pigment), 
which  is  especially  manufactured  for  another  (patented)  carbon  process, 
is  also  suitable  for  this  process. 

When  dry,  this  paper  is  immersed,  in  subdued  light,  in  a  solution  of 

Sesquichloride  of  Iron,  .    .    10  parts.  \ 

Tartaric  Acid,  3  parts.  >    .    .  (114). 

Water,  100  parts.  ) 


78 


MODERN  HELIOGRAPHIC  PROCESSES. 


and  dried  again  in  the  dark.  The  film  on  the  paper,  so  prepared,  is 
insoluble  in  hot  water;  but,  after  having  been  exposed  to  the  action  of 
light,  it  has  lost  this  property,  and  is  then  soluble.  If  such  paper  is 
exposed  under  a  tracing  or  line-drawing,  and  then  immersed  or  floated, 
upside  down,  in  a  tray  containing  hot  water,  the  film  will  dissolve  in 
all  parts  except  those  where  the  black  lines  of  the  tracing  prevented 
the  light  from  acting,  and  a  positive  copy,  in  black  lines  upon  a  white 
surface,  will  result. 

6.  Poitevin's  Process  by  means  of  which  Positive  Copies  in  Printing 
Ink  are  Received  from  a  Tracing  in  Black  Lines. 

Paper  coated  with  gelatine  (without  a  pigment)  is  sensitized  in  the 
same  solution  as  in  the  foregoing  process.  After  having  been  exposed  to 
the  action  of  light,  the  print  is  immersed  in  cold  water,  wherein  the  parts 
upon  which  the  light  did  act  will  absorb  water  and  swell  up.  Then  the 
print  is  placed  upon  a  glass  plate,  or  straight  board,  superficially  dried, 
and,  by  means  of  a  leather  roller,  is  inked  with  a  fatty  printing  ink.  Those 
places  only  upon  which  the  light  did  not  act  will  take  up  the  ink ;  the 
other  parts,  which  absorbed  the  water,  will  repel  it,  and  a  positive  copy 
will  result  from  a  positive  tracing. 

7.  Dr.  Zoellner's  Iodide  of  Starch  Process. 

In  May,  1863,  Dr.  F.  Zoellner  read,  before  the  Berlin  Polytechnic 
Society,  a  paper  on  the  following  simple  and  cheap  process  for  repro- 
ducing engravings,  drawings,  manuscripts,  etc.,  invented  by  him : 

Thin  and  smooth  paper,  of  a  uniform  texture,  is  first  to  be  sized 
with  starch.  If  paper  which  was  sized  with  starch  in  its  manufacture 
is  used,  this  operation  is  not  necessary.  When  dry,  the  paper  is  sen- 
sitized with  a  mixture  of 

Concentrated  Sol.  of  Sesquichloride  of  Iron,    1  volume.  \ 
Concentrated  Solution  of  Ferric  Oxalate,  .    .    6  volumes.  >    .    .  (115). 
Distilled  Water,  13  volumes.  ) 

This  solution  may  be  preserved  in  a  dark  place,  and  in  a  well-stoppered 
bottle,  for  a  long  time.  Floating  the  paper  upon  the  solution,  for  from 
30  to  60  seconds,  is  the  best  method  of  sensitizing  in  this  process.  The 
prepared  paper  may  be  preserved,  in  a  portfolio,  protected  from  light, 
for  over  2  weeks,  without  losing  its  sensitiveness. 

The  exposure,  through  thin  and  translucent  originals,  requires,  in  the 
sun,  but  a  few  minutes;  in  diffused  light,  from  J  to  -J  hour. 

The  image  is  invisible  after  the  action  of  light;  but  it  appears  at 
once,  intensely  blue,  by  treating  it  with  a  solution  of  iodide  of  potassium 
in  diluted  albumen. 

The  developing  solution  is  prepared  as  follows : 


PLATINUM  PROCESS  WILLIS'S  PATENT. 


79 


The  whites  of  two  eggs  are  beaten  to  froth,  and  allowed  to  stand  sev- 
eral hours ;  then  the  liquid  albumen,  which  has  collected  at  the  bottom 
of  the  vessel,  is  decanted,  and  diluted  with  one  third  of  its  volume  of 
distilled  water.  In  this  diluted  solution  of  albumen,  78  grains  troy  of 
iodide  of  potassium  are  dissolved. 

The  developing  solution  is  applied  by  means  of  a  wide  varnishing 
brush,  and,  before  it  is  dry,  is  washed  off  with  clean  water. 

The  prints  may  be  developed  as  soon  as  they  are  taken  out  of  the 
printing  frame,  or  this  operation  may  be  postponed  for  from  6  to  12  hours. 
The  developed  and  washed  prints  are  to  be  dried  in  the  open  air. 

8.  The  Platinum  Process. 

According  to  Pizzighelli  and  Huebl,  all  platinum  salts  are,  in  the 
presence  of  organic  substances,  sensitive  to  light — that  is  to  say,  they 
are  reduced  in  the  light.  Nevertheless,  the  following  processes  must  be 
classified  with  iron  prints,  as  a  ferric  salt,  and  not  a  salt  of  platinum,  is 
the  principal  sensitive  substance. 

Mr.  William  Willis,  Jr.,  was  the  first  inventor  of  a  successful,  prac- 
tical platinum  process,  after  a  number  of  investigators  had  made  a 
variety  of  interesting  but  imperfect  discoveries.  Mr.  Willis  found  that 
certain  salts  of  platinum  are  reduced  to  a  metallic  condition  by  a 
solution  of  ferrous  oxalate  in  oxalate  of  potassium.  The  sensitizing 
solution  applied  contains  chloroplatinite  of  potassium  and  ferric  oxalate. 
The  prepared  paper  has  a  lemon-yellow  color.  After  exposure  to  the 
action  of  light,  a  faint  picture  is  visible.  In  those  portions  of  the 
print  which  were  affected  by  the  light,  the  ferric  oxalate  has  been 
reduced,  partly  or  wholly,  to  ferrous  oxalate,  while,  in  the  parts  on  which 
the  light  did  not  act,  the  ferric  oxalate  remains  unaltered.  The  picture 
is  developed  by  being  floated  on  a  hot  solution  of  potassic  oxalate. 
This  bath  produces,  in  the  film,  a  concentrated  solution  of  a  platinum 
salt,  and  the  reducing  power  of  the  nearly  insoluble  ferrous  oxalate 
comes  into  action.  The  following  is  an  abstract  of  one  of  Willis's  patents. 
His  earlier  patent  bears  the  date  February  8,  1876. 

The  firm  of  Willis  &  Clements,  No.  1112  Hunter  Street,  Philadelphia, 
Pa.,  are  the  proprietors  of  Willis's  patents.  They  furnish  the  materials 
required  for  this  process,  and  sell  licenses  to  work  the  same. 

William  Willis,  Jr.'s,  Photo-Chemical  Printing. 

Abridgment  of  U.  S.  Patent  No.  213,484,  dated  March  18,  1879. 

According  to  the  said  invention,  I  proceed  as  follows :  That  is  to 
say,  I  coat  paper  with  an  aqueous  solution,  which  I  term  the  "  coating 
solution,"  each  fluid  ounce  of  which  contains  15  grains  potassic 
chloroplatinite,  or  double  chloride  of  potassium  and  platinum,  70  grains 


80 


MODERN  HELIOGRAPHIC  PROCESSES. 


ferric  oxalate,  or  oxalate  of  iron  (with  enough  oxalic  acid  to  render 
this  ferric  oxalate  freely  soluble),  and  2  grains  of  plumbic  chloride,  or 
chloride  of  lead.  I  then  dry  the  paper,  and  expose  it  to  light,  under 
or  behind  the  negative,  or  other  object,  from  which  the  picture  or  image 
is  to  be  produced  on  the  so-prepared  paper.  On  removing  the  paper  from 
this  negative,  or  other  object,  an  image  or  picture  is  usually  faintly 
visible.  I  then  float  the  said  paper,  face  downward,  on,  or  immerse  it 
in,  a  hot  aqueous  solution,  which  I  term  the  "developing  solution," 
each  fluid  ounce  of  which  contains  120  grains  potassic  oxalate,  or 
oxalate  of  potash,  and  7  grains  potassic  chloroplatinite,  or  double 
chloride  of  potassium  and  platinum.  This  solution  quickly  deepens  in 
color,  or  blackens,  the  picture  or  image  produced  on  the  coated  paper 
by  the  action  of  light.  I  then  wash  the  paper  in  a  weak  solution  of 
some  acid  (preferably  oxalic  acid),  and  finish  by  washing  it  in  plain 
water. 

For  coating  or  treating  the  paper,  or  other  surface,  previous  to  its 
insolation  or  exposure  to  light,  I  may  use  other  salts  of  platinum,  or 
salts  of  other  metals  than  those  above  named  —  such  as  salts  of  gold, 
of  iridium,  or  of  palladium,  or  mixtures  of  these  with  other  salts ;  but 
it  is  essential,  in  all  cases,  that  ferric  oxalate  form  one  of  the  ingre- 
dients or  constituents  of  the  coating  or  coatings  applied  to  the  said 
surfaces. 

The  following  are  examples  of  the  manner  in  which  I  vary  the 
composition  of  the  coating  solution  or  solutions : 

1st.  I  sometimes  substitute  15  grains  of  iridium  chloride  for  the 
potassic  chloroplatinite  used,  as  above  specified.  All  other  operations 
the  same. 

2d.  In  some  instances,  I  proceed  as  in  the  first-described  method, 
but  substitute,  for  the  2  grains  plumbic  chloride,  4  grains  mercuric 
chloride ;  the  treatment  being  otherwise  conducted  as  in  the  first- 
described  method. 

3d.  In  other  cases,  I  omit  the  plumbic  chloride  in  the  coating  com- 
pound or  solution. 

Instead  of  effecting  the  coating  of  the  paper,  or  other  surface,  with 
the  aforesaid  salts,  by  using  the  same  all  in  one  solution,  I  may,  in 
some  instances,  find  it  desirable  to  apply  such  salts  in  different  and 
successive  solutions,  and  dry  the  paper,  if  necessary,  between  the  suc- 
cessive coatings. 

Claims — 1.  The  process  herein  described,  of  producing  photographic 
pictures  by  coating  the  surface  of  paper,  wood,  or  other  material,  with  a 
compound  consisting  of  the  double  chloride  of  potassium  and  platinum 
and  oxalate  of  iron,  exposing  the  material  thus  prepared  under  a 
negative,  and  developing  and  toning  the  image  by  means  of  a  solution 


PROCESSES  WITH  SALTS  OF  IRON  PLATINUM  PROCESSES. 


81 


of  oxalate  of  potash  and  the  double  chloride  of  potassium  and  plat- 
inum, substantially  as  specified. 

2.  A  sensitive  coating,  for  the  production  of  photographic  pictures, 
consisting  of  the  double  chloride  of  potassium  and  platinum,  or  other 
similar  salt,  and  oxalate  of  iron  dissolved  in  oxalic  acid,  substantially 
as  specified. 

3.  A  developing  and  toning  compound,  for  photographic  pictures 
produced  upon  the  sensitive  compound  herein  mentioned,  consisting  of 
oxalate  of  potash  and  the  double  chloride  of  potassium  and  platinum, 
substantially  as  specified. 

Pizzighelli's  and  Huebl's  Recipes. —  In  the  year  1882,  the  Photo- 
graphic Society  of  Vienna  awarded  the  Voigtlaender  medal  in  gold  to  a 
treatise  on  "The  Platinotypy,"  written  by  Captain  Joseph  Pizzighelli 
and  Captain  A.  Baron  Huebl.  From  the  practical  part  of  this  work, 
we  select  the  following  recipes  and  remarks : 

The  paper  must  not  be  too  thin,  or  tinted  blue  with  ultramarine, 
because  such  paper  becomes  yellow  in  the  acid  bath.  Paper  tinted 
with  cobalt-blue  is  the  most  suitable.  The  paper  mill  in  Rives  manu- 
factures paper  which  is  especially  adapted  for  platinum  prints.  The 
paper  must  be  coated  with  a  gelatine  or  arrow-root  solution,  or  the 
like.  The  strength  of  such  a  sizing  solution  depends  upon  the  sizing 
which  the  paper  already  has,  as  the  pores  of  the  paper  should  not  be 
entirely  closed.  A  gelatine  coating  imparts  to  the  prints  a  bluish-black 
tone;  an  arrow-root  sizing,  a  brown-black  tone.  The  following  solu- 
tions are  suitable  for  Rives  paper : 


The  gelatine  is  left  in  the  cold  water  for  about  half  an  hour,  in 
order  to  swell  up;  then  the  water  is  poured  off,  and  heated  to  about 
140°  F.  The  gelatine  is  then  put  into  the  water,  and,  when  it  has  dis- 
solved, the  alum,  and  then  the  alcohol,  is  added.  Finally,  the  solution 
is  filtered,  through  a  piece  of  clean  linen  or  muslin,  into  a  porcelain 
or  other  tray,  which  is  a  little  larger  than  the  sheets  to  be  sized.  In 
a  warm  room  (at  65°  F.),  the  solution  will  not  become  torpid.  The 
paper  may  be  floated  upon  the  solution,  or  immersed  in  the  same.  In 
order  to  immerse  the  sheets  conveniently,  the  solution  must  cover  the 
bottom  of  the  tray  to  the  depth  of  at  least  lyV'. 

The  addition  of  the  alum  makes  the  gelatine  insoluble  after  drying. 
The  alcohol  prevents  the  formation  of  air-bubbles,  to  a  certain  extent. 


Gelatine  Solution. 


Phototype  Gelatine,    ...    10  parts.  ^ 

Water,   800  parts. 

Alum,  3  parts.  | 

Alcohol,   200  parts.  J 


82 


MODERN  HELIOGRAPHIC  PROCESSES. 


Arrow-root  Solution. 

Arrow-root  Flour,  ....    10  parts.  \ 

Boiling  Water,   800  parts,  i    .    .  (117). 

Alcohol,   200  parts.  ) 

The  arrow-root  is  ground  in  a  mortar,  with  a  little  cold  water,  and 
then,  while  constantly  stirring,  poured  into  the  boiling  water;  after  a 
few  ebullitions,  the  vessel  is  taken  from  the  fire,  the  alcohol  added,  and 
the  solution  decanted  into  a  dish. 

In  preparing  paper  with  arrow-root  or  with  gelatine,  it  should  first 
be  immersed  with  that  side  down  which  is  to  become  the  picture-side, 
then  turned  over,  and  air-bubbles  carefully  removed.  The  paper  may 
remain,  for  2  to  3  minutes,  in  the  solution;  then  it  should  be  taken 
out,  with  a  swift  motion,  and  hung  up  to  dry.  The  room  must  be  warm 
enough,  so  that  the  gelatine  drops  off,  and  does  not  collect  and  solidify 
at  the  edge  of  the  paper.  When  the  paper  is  dry,  the  operation  must 
be  repeated,  and  the  paper  hung  up  to  dry,  in  a  reverse  position  from 
that  in  which  it  was  suspended  the  first  time.  This  must  be  done  in 
order  to  distribute  the  coating  more  uniformly. 

Linen  and  other  fabrics  are  treated  in  the  same  manner  as  paper, 
but,  after  the  second  sizing,  they  should  be  stretched  in  a  frame,  to 
which  they  may  be  fastened  with  thumb-tacks. 

Wood  is  to  be  planed  and  sand-papered,  and  then  coated  repeatedly 
with  a  3  per  cent,  arrow-root  solution,  until  it  ceases  to  absorb  the 
liquid. 

Stock  Solutions. 

A.  — Chloroplatinite  Solution. 

Chloroplatinite  of  Potassium,  .  .  1  part.  )  (lip.) 
Distilled  Water,  6  parts.  )  '    "    *  ;' 

This  solution  is  perfectly  air  and  light  resisting.  The  platinum  salt 
must  be  made  by,  or  bought  of,  a  chemist.  It  may  be  tested  for  pureness 
in  two  ways :  1.1  part  of  the  salt  must  be  perfectly  soluble  in  6  parts 
of  water;  2.  Such  solution  must  have  no  acid  reaction. 

B.  — Normal  Ferri-Oxalate  Stock  Solutions. 

To  a  solution  of  ferric  oxalate,  containing,  per  fluid  ounce,  1-J 
drams,  or  90  grains  troy,  of  ferric  oxalate  [^2(^2^4)3]' 

Add  so  much  (solid)  crystallized  oxalic  acid  that,  together  with  f  (119). 
the  free  acid  already  in  the  solution,  it  amounts  to  from 
6  to  8  per  cent,  of  the  ferric  oxalate. 

The  commercial  ferric  oxalate  solution  may  be  tested  with  a  solution  of 
red  prussiate  of  potash,  which  ought  not  to  produce  a  blue  coloration; 


PLATINUM  PROCESSES. 


83 


and  by  boiling  and  diluting  the  solution  with  ten  volumes  of  distilled 
water,  whereby  it  should  remain  clear.  The  first  test  will  detect  the 
presence  of  a  ferrous  salt;  the  second,  that  of  a  basic  ferric  oxalate. 
Ferric  oxalate,  in  solid  form,  can  not  be  prepared  so  as  to  have  the 
same  composition  every  time. 

C. — Normal  Chlorate  of  Potassium  with  the  Ferric  Oxalate  Stock  Solution  : 

Stock  Solution  B,     ...    8  fluid  ounces.  )  (-[or\\ 
Chlorate  of  Potassium,  .    .15  grains  troy.  ) 

Solutions  B  and  C  must  be  preserved  with  perfect  exclusion  of  light. 


Sensitizing  Solutions. 

A. — Normal  Solution  : 

Platinum  Solution  A,     ....  24  volumes.  \ 

Ferric  Oxalate  Solution  B,     .    .  22  volumes.  >  .  (121). 

Distilled  Water,  4  volumes.  ) 

This  solution  produces  soft  effects  and  deep  blacks.  For  well-sized  and 
highly-calendered  paper  the  water  may  be  omitted. 


B.  — Solution  for  obtaining  results  having  the  character  of  silver  prints : 

Platinum  Solution  A,  24  volumes. 

Ferric  Oxalate  Solution  B,  .  .  .14  volumes. 
Chlorate-containing  Solution  C,  .  8  volumes. 
Distilled  Water,  4  volumes. 

C.  — Solution  for  the  reproduction  of  drawings,  engravings,  etc. : 

Platinum  Solution  A,  24  volumes.  \ 

Chlorate-containing  Solution  (7,     .  22  volumes.  >  .  (123). 
Distilled  Water,  4  volumes.  ) 

If  pencil  drawings  are  to  be  reproduced,  or  when  perfectly  black  lines 
are  not  desired,  the  solution  may  be  diluted  with  an  equal  volume  of 
water. 

Sensitizing. — The  paper  is  stretched  over  a  glass  plate,  which  is  held 
in  position  by  four  strips  of  wood  nailed  to  a  board.  The  corners  of  the 
glass  plate  are  cut  off  obliquely.  The  stretching  of  the  paper  is  effected 
by  means  of  four  india-rubber  straps,  which  are  fastened  to  wooden 
clamps.  Each  corner  of  the  paper  being  gripped  by  a  clamp,  the  other 
ends  of  the  rubber  straps  are  attached  to  the  board  by  means  of  hooks, 
so  that  the  straps  stretch  the  paper  in  the  direction  of  the  diagonals. 


84 


MODERN  HELIOGRAPHIC  PROCESSES. 


Small  sheets  of  paper  may  be  fastened  to  a  straight  drawing-board  by 
means  of  thumb-tacks. 

The  sensitizing  solution  must  be  mixed  immediately  before  use, 
because  it  gradually  decomposes,  even  in  the  dark.  For  paper  of  the 
above-mentioned  quality, 

1  fluid  ounce  of  sensitizing  solution  will  cover  10^-  square  feet  of  paper. 
1  fluid  dram  "  "  "       190  square  inches  of  paper. 

1  minim  "  "  "  3.15  " 

6  minims  "  "  "        19  " 

For  copies  on  paper,  linen,  or  wood,  on  which  deep-black  prints  are 
wanted,  it  may  be  estimated  that,  for  every  1,000  square  inches  of  super- 
ficial area,  2  to  2-J  grains  troy  of  the  solid  chloroplatinite  of  potassium 
are  required;  or,  for  every  100  square  feet  of  surface,  29  to  36  grains 
troy  of  the  salt.  The  sensitizing  solution  may  be  applied  by  means 
of  a  flannel  pad,  or  with  a  soft  bristle  brush,  but  the  latter  must  not 
be  mounted  or  bound  in  metal. 

The  sensitizing  is  best  done  in  weak  daylight,  because,  in  yellow 
lamplight,  it  is  difficult  to  see  whether  any  portion  of  the  paper  is  left 
uncovered  by  the  yellow  liquid.  The  flannel  pad  must  be  renewed  every 
15  minutes,  or  the  brush  washed,  from  time  to  time,  in  clean  water. 
As  soon  as  the  dampness  on  the  surface  has  disappeared,  the  sensitized 
sheet  is  hung  up  in  a  dark  room,  near  the  stove,  or  in  a  drying  box,  to 
be  thoroughly  dried  at  a  temperature  of  from  86°  to  104°  F.  The  dry- 
ing ought  not  to  take  longer  than  ten  minutes.  Absolute  dryness  of  the 
paper  is  an  indispensable  condition,  in  order  to  obtain  fine  prints.  The 
paper  must  be  kept  absolutely  dry  before,  during,  and  after  exposure  to 
light.  For  this  purpose,  it  is  put  into  a  tubular  box,  at  the  bottom  of 
which  a  smaller  perforated  box,  containing  calcium  chloride,  has  been 
placed.  The  latter  is  wrapped  in  mull.  In  case  a  part  of  the  chloride 
of  calcium  should  become  wet,  it  must  be  taken  out,  and  placed  on  a 
shovel,  and  dried  on  a  stove,  or  over  a  fire,  then  wrapped  again  and 
replaced.  Care  must  be  taken  that  no  particle  of  the  calcium  gets 
into  the  main  box,  or  comes  in  contact  with  the  paper.  It  is  well  to 
always  have  some  dry  chloride  of  calcium  on  hand,  to  substitute  at  once 
for  such  as  may  have  become  wet.  In  order  to  keep  the  paper  dry 
in  the  printing  frame,  a  sheet  of  india-rubber  cloth  may  be  placed 
between  the  blanket  and  the  lid.  Should  any  moisture  remain,  the  paper 
will  lose  a  part  of  its  sensitiveness,  the  prints  obtained  will  not  be 
clear  and  distinct,  and  the  white  parts  will  not  be  pure. 

Copying. — The  copying  requires,  in  this  process,  more  attention  than 
in  other  processes.  The  impression  of  the  light  produces  a  relatively 
weak,  but  distinctly  visible  image.  The  yellow  color  of  the  paper  changes, 
in  the  light,  at  first  to  brown,  and  then  again  becomes  lighter  (orange- 


PLATINUM  PROCESSES. 


85 


colored),  so  that  the  deepest  shadows  of  a  picture  appear  lighter  than 
the  medium  tints.  After  exposure  to  light,  the  prints  may  be  developed 
at  once,  or  preserved  in  a  calcium  box  until  evening.  It  is  of  importance, 
however,  that  the  chloride  of  calcium  should  not  be  allowed  to  come 
in  contact  with  the  paper,  as  this  would  cause  yellowish-white  spots  in 
the  finished  prints. 

The  Developing  Solution  is  a  cold,  saturated  and  acidified  solution  of 
oxalate  of  potassium,  which  is  heated  to  from  176°  to  185°  F. 

Developing. —  Small  prints  may  be  placed  in  a  tray,  and  the  hot 
developing  solution  poured  over  them.  For  large  prints  this  method 
is  not  practicable,  and  the  application  of  a  guttered,  enameled  iron  tray 
is  to  be  preferred.  A  developing  tray,  of  this  kind,  is  placed  in  another 
vessel,  which  is  a  little  larger  than  the  tray,  and  serves  as  a  water-bath. 
It  may  be  made  of  zinc  or  of  galvanized  iron.  The  water  for  the 
second  vessel,  and  the  oxalate  of  potassium  solution,  may  be  heated,  in 
other  vessels,  on  a  stove,  or  over  a  flame,  and  poured,  while  hot,  into 
the  apparatus.  A  small  gas  flame,  or  an  alcohol  lamp,  is  sufficient  to 
maintain  the  temperature  of  the  developer,  especially  when  the  tray  is 
fitted  with  a  cover  —  which  may  be  made  of  zinc  or  galvanized  iron. 
The  tray  must  be  a  little  longer  than  the  width  of  the  widest  print. 
In  order  to  develop  a  print,  the  cover  is  taken  from  the  tray,  and  the 
print  drawn  slowly  through  the  developer.  The  action  takes  place  at 
once,  and  the  brown,  or  orange,  color  of  the  print  is  converted  into  a 
deep  black. 

In  order  to  protect  the  fingers,  the  print  is  taken  hold  of,  at  two 
corners,  by  means  of  horn  or  bone  pincers.  If  parts  of  the  print  should 
not  come  in  contact  with  the  oxalate  solution  —  for  instance,  in  conse- 
quence of  air-bubbles  —  the  print  may  be  drawn,  a  second  time,  through 
the  solution.  Over-exposed  prints  can  often  be  saved  by  lowering  the 
temperature  of  the  developer;  under-exposed  ones,  by  increasing  the 
heat  of  the  same — if  necessary,  to  the  boiling  point. 

It  should  again  be  remembered  that  the  developer  must  have  an  acid 
reaction.  It  should,  therefore,  be  tested,  from  time  to  time,  with  litmus 
paper,  and,  when  found  necessary,  be  acidified  with  oxalic  acid. 

After  having  been  used,  the  developer  is  poured  into  a  bottle,  and 
may  be  used  over  and  over  again.  When  crystals  commence  to  form, 
the  evaporized  water  is  to  be  replaced ;  and  when  the  quantity  becomes 
too  small,  fresh  oxalate  of  potassium  solution  is  to  be  added. 

The  developer  must  also  be  kept  in  a  dark  place. 

Finishing  the  Prints. — Immediately  after  being  developed,  the  prints 
are  immersed  in  an  acid  bath,  composed  of 


Hydrochloric  Acid, 
Water,  .... 


1  part.  ) 
80  parts.  ) 


86 


MODERN  HELIOGRAPHIC  PROCESSES. 


and  left  therein,  until  all  of  the  iron  salt,  that  may  be  in  the  paper,  has 
been  completely  removed.  The  diluted  acid  must  be  replaced  as  often 
as  it  shows  the  slightest  yellow  tinge.  If  the  prints  are  left,  for  about 
10  minutes,  in  each  acid  bath,  the  latter  must  generally  be  replaced 
3  times. 

Finally,  the  prints  are  washed  for  10  or  15  minutes  in  water, 
which  must  also  be  renewed  several  times,  in  order  to  remove  the 
muriatic  acid;  then  they  are  hung  up  to  dry. 

Prints  on  Wood  or  Linen  are  treated  in  the  same  manner  as  those  on 
paper. 

Captain  Pizzighelli's  New  Platinotype  Process  without  Devel- 
opment.—  The  importance  of  the  modifications  of  Pizzighelli's  direct 
platinotype  process,  now  to  be  described,  will  be  apparent  when  we  state 
that  the  old  iron  solution  —  so  different  and  troublesome  to  prepare — is 
no  longer  necessary,  its  place  being  taken  by  a  double  oxalate  of  sodium 
and  iron  (sodium-ferric  oxalate). 

Captain  Pizzighelli  says :  In  relation  to  my  recent  memoir  on  the 
"  Direct  Platinotype  Process,"  I  remarked,  that,  in  all  probability,  some 
of  the  definite  double  salts  of  ferric  oxalate  might  be  employed;  and, 
since  that  time,  I  have  continued  my  experiments  in  this  direction,  not 
only  with  double  salts  prepared  by  myself,  but  also  with  samples 
obtained  from  the  firm  of  Schuchardt,  in  Goerlitz.  The  result  must  be 
considered  as  very  satisfactory,  and,  as  far  as  simplicity  goes,  the  method 
leaves  nothing  to  be  desired. 

Of  the  double  salts  experimented  with,  the  sodium-ferric  oxalate 
proved  the  most  satisfactory,  the  corresponding  potassium  salt  giving 
less  sensitiveness;  while  the  ammonium  salt,  although  giving  greater 
sensitiveness,  gives  less  brilliant  images  than  the  sodium  salt,  and, 
moreover,  images  having  a  tendency  to  a  cold,  bluish  tone.  Still,  for 
very  hard  negatives,  and  in  the  reproduction  of  pencil  drawings,  the 
ammonium  salt  may,  perhaps,  occasionally  be  used  with  advantage. 

In  the  preparation  of  the  sensitive  paper,  considerable  variation  is 
allowable,  and  the  following  three  methods  give  results  which  are  nearly 
identical. 

First  Method. —  Arrow-root  paste  is  prepared  with  1  part  of  arrow- 
root and  10  parts  of  water,  and,  when  this  is  cold,  it  is  applied  to  the 
paper  with  a  sponge  —  one  sheet,  18"X  22-J-",  requiring  from  15  to  20 
grammes  (4  to  5  drams)  of  the  paste.  When  the  paste  has  been  well 
distributed  with  the  sponge,  it  is  equalized  and  smoothed  with  a  badger 
softener,  and  the  sheet  is  hung  up  to  dry.  After  drying,  the  process 
is  repeated,  and  the  sheet  is  again  dried.  To  coat  it  smoothly,  a  sheet 
takes  about  5  minutes.     The  arrow-root  paper  can  be  stored,  for  use, 


PROCESS  WITHOUT  DEVELOPMENT. 


87 


in  a  dry  place,  when  it  is  sensitized  with  a  preparation  made  in  the 
manner  about  to  be  described. 

Four  solutions  are  required :  A,  B,  C,  and  D. 


A. — Chloroplatinite  of  Potassium,     ...    1  part. 
Distilled  Water,  6  parts. 


(125). 


B.  — Sodium-ferric  Oxalate,   40  parts.  ) 

Sodium  Oxalate  Solution  (3  per  cent.)  100  parts.  >  .  (126). 
Glycerine,*  3  parts.  ) 

In  preparing  the  solution  B,  the  sodium  oxalate  solution  is  warmed  to 
about  40°  or  50°  C.  (104°  or  122°  F.),  and  then  the  sodium-ferric 
oxalate  is  dissolved  in  it.  On  cooling,  a  little  saline  matter  separates; 
so  nitration  is  necessary. 

C.  — Solution  B,  100    parts.  )  /i97^ 

Potassium  Chlorate,  0.4  parts.  ) 

D.  — Mercuric  Chloride  Solution  (5  per  cent.)  20    parts.  \ 

Sodium  Oxalate  Solution  (3  per  cent.)  40    parts.  >  .  (128). 
Glycerine,  1.8  parts.  ) 

For  sensitizing  a  sheet  (demy  size)  of  300  square  inches,  when  black 
tones  are  desirable,  we  must  take 

Solution  A,     ...    5  millilitres  =  80  minims.  J 
Solution  B,     .    .    .    6  millilitres  =  96  minims.  [  .  (129). 
Solution  O,     ...    2  millilitres  =  32  minims.  ) 

For  hard  negatives,  the  quantity  of  solution  C  must  be  diminished,  and 
B  must  be  increased  to  the  same  extent;  whereas,  for  specially  soft 
negatives,  the  reverse  holds  good. 

For  brown  tones,  the  following  is  used : 

Solution  A,  80  minims.  \ 

Solution  B,  64  minims,  i  .  (130). 

Solution  O,  64  minims.  ) 

The  above  sensitizing  solution  gives  a  sepia-brown  tone,  and  inter- 
mediate tints  can  be  obtained  by  increasing  the  proportion  of  C,  and 
correspondingly  diminishing  D. 

The  application  of  the  sensitizing  solution  to  the  paper  is  effected 
by  means  of  a  suitable  brush  (not  tin-mounted),  followed  by  the  use  of 
the  softener  as  before.  The  sheet  is  then  dried,  at  about  86°  or  104°  F. 
(30°  or  40°  C.) 

*The  addition  of  glycerine  to  this  and  the  following  solutions  is  only  necessary  in 
very  dry  weather. 


88 


MODERN  HELIOGRAPHIC  PROCESSES. 


Second  Method. — In  this  method,  the  sodium  oxalate  —  in  fact,  the 
developing  agent — is  not  added  to  the  iron  solution,  but  mixed  with 
the  arrow-root  used  for  sizing;  and  the  arrow-root  paste  used  has  the 
following  composition : 

Arrow-root,   2  parts. 

Sodium  Oxalate  Solution,  containing  3  per  cent.,  100  parts. 


(131). 


The  method  of  coating  the  paper  with  the  starch  paste  is  the  same 
as  already  described. 

Sensitizing  the  Paper. — The  solutions  A,  B,  C,  and  2),  used,  have  the 
same  composition  as  in  the  case  of  the  first  method,  only  the  iron 
solution  B  is  made  up  with  water,  instead  of  sodium  oxalate  solution. 

In  order  to  prevent  mistake,  the  series  is  given  below  as  A2y  B2, 
C2,  and  D2 : 


A 2- — Potassium  Chloroplatinite,     ....    1  part. 
Distilled  Water,  6  parts. 

B2. — Sodium-ferric  Oxalate,  4  parts. 

Distilled  Water,     .    .  10  parts. 

C2. — Solution  B2,  100  parts. 

Potassium  Chlorate,  0.4  parts. 


.(132). 
.(133). 
.(134). 


D2. — Mercuric  Chloride  Solution  (5  per  cent),  20    volumes.  \ 

Sodium  Oxalate  Solution  (3  per  cent.),  40    volumes.  >  .  (135). 
Glycerine,  1.8  volumes.  ) 

The  general  directions,  as  to  the  series  A,  B,  C,  and  D,  apply  equally 
to  the  preparation  and  use  of  the  series  A2)  B2}  C2,  and  D2. 

Third  Method. — This  method  is  a  simplification,  as  the  sizing  of  the 
paper  is  not  a  separate  operation,  the  thickening  material  being  mixed 
with  the  sensitizing  preparation.  For  this  method,  four  solutions,  which 
are  designated  A3,  Bs,  (73,  and  D3,  must  be  prepared,  and  the  composi- 
tion of  these  solutions  is  as  follows : 


Az. — Potassium  Chloroplatinite,      ....    1  part. 
Distilled  Water,  6  parts. 

Bz. — Sodium-ferric  Oxalate,  ......    40  parts.  > 

Powdered  Gum  Arabic,  40  parts. 

Solution  of  Sodium  Oxalate  (3  per  cent.)  100  parts. 
Glycerine,  3  parts. 


(136), 


^.(137). 


To  prepare  2?3,  the  sodium  oxalate  solution  is  first  heated  to  40°  or  50° 
C.  (104°  or  122°  F.),  when  the  iron  salt  and  glycerine  are  stirred  in. 


PIZZIGHELLI'S  PLATINUM  PROCESS. 


89 


After  the  former  is  completely  dissolved,  the  solution  is  transferred  to 
a  mortar,  when  the  gum  is  gradually  added,  and  thoroughly  incor- 
porated. This  being  done,  the  mixture  is  allowed  to  stand  at  rest,  for 
some  hours,  in  order  that  small  agglomerations  of  gum  may  thoroughly 
dissolve,  after  which  the  whole  is  again  incorporated,  and  then  squeezed 
through  a  cloth. 

C3. — Solution  i>3,    .  . 
Potassium  Chlorate, 

Dz. — Mercuric  Chloride  Solution  (5  percent.),  20  parts. 
Sodium  Oxalate  Solution  (3  per  cent.),  40  parts. 

Powdered  Gum  Arabic,   24  parts. 

Glycerine,   1.8  parts. 

Solution  D3  is  mixed  in  a  similar  way  to  that  recommended  in  case 
of  Bs. 

The  proportions  in  which  A%,  i?3,  C3,  and  Dz  are  to  be  mixed  for 
use  are  analogous  to  those  of  the  first  method,  and  the  following  may 
be  mentioned  as  suitable  for  black  images  under  ordinary  conditions : 

Az. — Platinum  Solution,       ....    5  volumes.  \ 

B3. — Iron  and  Gum  Solution,   ...    5  volumes.  >  .  (140). 

(73. — Gum  and  Chlorate  Solution,     .    2  volumes.  ) 

When,  however,  sepia-brown  images  are  required,  the  following  may  be 
used : 

Az. — Platinum  Solution,  5  volumes.  \ 

(73. — Gum  and  Chlorate  Solution,     .    4  volumes.  >   .  (141). 
D3. — Mercuric  Iron  and  Gum  Solution,  4  volumes.  ) 

The  application  of  the  mixture  is  made  with  the  brush,  according  to 
the  instructions  already  given,  and  during  the  application  numerous 
small  bubbles  are  formed;  but  these  can  be  disregarded,  as  they  disap- 
pear completely  when  the  coating  is  smoothed  with  the  badger  softener. 
The  gum  layer  dries  with  a  light  gloss,  but  no  particular  precautions 
are  necessary  in  drying. 

It  should  be  mentioned,  that  the  third  method  appears  to  be,  on  the 
whole,  the  most  convenient,  and  the  most  worthy  of  recommendation. 

After  drying,  the  paper  should  be  preserved  in  the  chloride  of  calcium 
box ;  but  the  paper  prepared  as  now  recommended  seems  to  be  far  less 
prone  to  alteration  than  that  prepared  by  the  older  methods,  as  speci- 
mens kept  for  10  days,  without  any  special  precautions,  gave  results 
quite  as  good  as  those  obtained  on  paper  which  had  been  kept  in  the 
chloride  of  calcium  box. 


100  parts. 
0.4  parts. 


(138). 


90 


MODERN  HELIOGRAPHIC  PROCESSES. 


Nothing  very  special  is  to  be  said  about  the  printing,  except  that 
the  action  of  the  light  must  go  on  until  the  image  shows  the  intensity  it 
should  have  when  finished  —  in  short,  there  should  be  no  over-printing. 

The  printing  being  finished,  the  paper  is  immersed  in  the  following : 

Hydrochloric  Acid,  1  volume.   )  c\ao\ 

Ordinary  Water,  80  volumes.  S 

This  solution  is  changed  two  or  three  times  —  in  fact,  until  it  shows 
no  further  trace  of  yellow  color  —  after  which  there  is  nothing  to  be 
done  but  to  wash  the  platinotype  print  in  water,  and  to  dry. 

Under-printed  images  may  be  developed  in  a  cold  solution  of  sodium 
or  potassium  oxalate;  and,  in  conclusion,  it  should  be  mentioned,  that 
the  iron  salt,  in  the  solid  form  —  as  also  its  solution,  and  the  mercuric 
solution  —  should  be  kept  in  the  dark. 

Photo  News. — Phil.  Photographer. — Photo.  Corresp. 


XL 


PROCESSES  WITH   SALTS  OF  CHROMIUM. 

The  chromic  salts,  which  are  used  in  heliography  (bichromate  of 
potassium  [K2Cr207]  and  bichromate  of  ammonium),  have  properties 
similar  to  those  of  the  ferric  salts.  When  a  chromate,  in  the  presence 
of  an  organic  substance,  is  exposed  to  the  action  of  light,  the  organic 
substance  takes  away  oxygen  from  the  chromate,  and  the  chromic  acid 
is  reduced  to  brown  chromo-chromic  oxide.  Certain  organic  substances, 
such  as  albumen,  gelatine,  sugar,  etc.,  hereby  alter  their  nature.  The 
heliographic  processes  with  chromium  salts  may  be  divided  into  two 
distinct  groups.  The  first  group  includes  those  processes  in  which 
either  the  reduced  or  the  unaltered  chromate  is  used  in  producing  the 
picture;  the  second  contains  all  those  processes  in  which  the  nature 
of  the  organic  substance,  either  in  the  altered  or  in  the  unchanged  parts, 
is  applied  in  forming  the  image. 

Those  prints  produced  by  a  process  of  the  first  group  —  in  which  the 
chromate  alone  forms  the  pale  image  —  may  be  intensified  or  toned  by 
various  re-agents.  Lead,  silver,  and  mercury  salts,  will  produce,  respec- 
tively, a  yellow,  red,  and  brown  color.  Certain  chromium  compounds, 
also,  act  as  mordants  for  fixing  certain  dye-stuffs,  such  as  alizarine, 
logwood,  yellow-wood. 

The  changes  in  the  nature  of  organic  substances,  which  are  caused 
by  chromates  when  they  are  reduced  by  light — and  which  are  made  use 
of  in  the  processes  of  the  second  group  —  are  the  following :  A  chromate, 
or  bichromate,  can  be  dissolved,  and  mixed  with  glue  or  gelatine  in  hot 
water,  or  with  gum  arabic  or  albumen  in  cold  water,  without  either  of 
these  substances  suffering  a  change  at  once,  on  account  of  the  chromic 
salt.  If  a  plate  of  glass,  or  a  sheet  of  paper,  be  coated  with  such  a 
solution,  and  allowed  to  dry  in  the  dark,  it  becomes  firm,  and  yet 
remains  soluble  in  water.  As  soon  as  the  film  is,  however,  influenced 
by  light,  and  the  chromate  is  reduced  to  a  chromic  oxide  salt,  the  film 
of  glue,  gelatine,  gum,  or  albumen  is  tanned  —  that  is  to  say,  is  made 
insoluble  in  water.  This  discovery  was  first  made  by  Fox  Talbot,  in 
1852,  and  applied  for  producing  steel-plate  engravings. 

If,  after  exposure  to  light,  a  sheet  of  paper,  that  has  been  coated 
with  chromated  gelatine,  is  rubbed  with  a  moist  sponge,  the  paper  will 
imbibe  the  water  at  those  places  on  which  the  light  had  not  been  able 
to  act.    It  is,  also,  a  singular  fact,  that,  if  printing  ink  is  then  applied, 

91 


92 


MODERN  HELIOGRAPHIC  PROCESSES. 


it  will  only  adhere  to  those  places  that  were  affected  by  the  light.  This 
fact  was  discovered  by  Poitevin,  the  meritorious  discoverer  in  photo- 
graphic chemistry. 

If  bichromated  gelatine,  or  gum,  is  mixed  with  sugar,  grape  sugar, 
honey,  or  glycerine,  and  a  sheet  of  paper,  or  a  plate  of  glass,  metal, 
porcelain,  or  the  like,  be  coated  with  such  a  solution,  and  dried,  the 
film  will  be  hygroscopic,  but,  if  exposed  to  light  under  a  drawing,  it  will 
lose  this  property  in  all  those  parts  which  were  not  protected  by  the 
opaque  lines  of  the  drawing,  and  upon  which  the  light  could  act.  If, 
now,  such  a  print  is  brought  to  a  damp  place,  or  breathed  upon, 
and  then  lampblack,  or  another  impalpable  powder,  is  dusted  over  the 
print,  the  powder  will  only  adhere  to  those  places  which  were  protected 
from  the  light  by  the  black  lines  of  the  drawing,  and  which  absorbed 
moisture. 

Upon  these  changes  in  the  nature  of  chromated  gelatine,  albumen, 
etc.,  not  only  a  large  number  of  heliographic  processes,  but  also  a  large 
number  of  photo-mechanical  printing  processes  —  such  as  Photo-lith- 
ography, Woodburytypy,  Artotypy,  Phototypy,  Pyrotypy,  etc. —  are  based. 

1.  Processes  in  which  the  Reduced  Chromate  Forms  the  Base  of 
the  Picture — Mungo  Ponton's  Chromium  Prints. 

Mungo  Ponton  was  the  first  'to  succeed  in  making  chromium  prints. 
He  published  his  discovery,  in  1839,  in  the  New  Philosophical  Journal. 
Ponton  saturated  paper  with  a  solution  of  bichromate  of  potash,  dried 
it  in  the  dark,  exposed  it  under  a  drawing,  and  fixed  by  washing  in 
water.  The  resulting  print  is  a  negative  in  white  lines  on  a  very  pale 
,  greenish-brown  ground.  According  to  Hunt  and  Burnett,  bichromate 
of  copper  furnishes  a  more  intensive  copy  than  bichromate  of  potassium. 
Such  bichromate  of  copper  prints  may  be  colored  reddish-brown  by  a 
solution  of  red  prussiate  of  potash.  Bichromate  of  copper  is  formed 
on  mixing  solutions  of  sulphate  of  copper  (blue  vitriol)  and  bichromate 
of  potassium.  A  brown  negative  print  may  be  obtained,  from  a  positive, 
on  paper  sensitized  with  the  solution  given  in  Haleur's  chromate  of 
silver  process,  by  developing  it  with  a  solution  of  red  prussiate  of 
potash. 

M.  Guard abasiti's  Process. — The  paper  is  sensitized  by  immersing 
the  same,  for  5  minutes,  in  a  cold  saturated  solution  of  bichromate  of 
potassium.  When  dry,  the  paper  is  exposed  to  light,  under  a  drawing 
(or,  if  a  positive  print  is  desired,  under  a  negative),  until  the  image  is 
visible  on  the  back  of  the  paper.  The  parts  affected  by  the  light  will 
look  reddish-brown.  Then  the  print  is  floated  on  water,  picture-side  up, 
until  all  the  chromic  salt,  which  was  not  altered  by  the  light,  is  dis- 
solved. 


CHROMIUM  PROCESSES  R.  B.  WEST'S  PATENTS. 


93 


Then  the  print  is  floated  upon  a  solution  of 

Saturated  Solution  of  Nitrate  of  Mercury,  4  parts.  \ 

Bichromate  of  Potassium,  1  part.   >  .  (143). 

Water,   28  parts.  ) 

The  solution  must  be  filtered,  and  be  made  some  time  before  it  is  used. 
It  must  have  a  greenish  color,  and  be  transparent.  The  print  is  floated 
upon  this  solution,  picture-side  down,  for  15  or  20  minutes,  until  it  has 
an  intensive  red  color,  and,  after  it  has  been  thoroughly  washed,  it  is 
immersed  in  diluted  ammonia  water,  consisting  of 


Strong  Ammonia  Water,  .1  part. 

Distilled  Water,  50  to  75  parts. 


•  (144). 


wherein  the  color  of  the  print  changes  to  brown.  The  print  is  washed 
again,  and  then  fixed  and  toned  dark  in  a  bath  of 


Chloride  of  Gold,  1  part. 

Dissolved  in  Distilled  Water,     .    .     7,500  parts. 


.  (145). 


Then  the  print  is  washed  in  water,  for  the  last  time,  dried,  and  finally 
varnished  with  a  solution  of 

Shellac,  8  parts.  )  (1Aa\ 

Alcohol,  100  parts.  )'    '   1  ;' 

Photo.  Mitth.,  Vol.  4. 


R.  B.  West's  Patents  on  Photographic  Printing. 
Abridgment  of  U.  S.  Patent  No.  273,206,  dated  February  27,  1883. 

First.  The  bath  for  rendering  the  paper  sensitive  to  light.  I  pre- 
pare a  bath  as  follows : 

Take  of  Potassium  Bichromate,  .    .    3  parts.  \ 

Magnesium  Sulphate,   1  part.  >    .  (147). 

Mercuric  Chloride  1  part.  ) 

Mix,  and  dissolve  in  the  smallest  quantity  of  boiling  water  required 
for  solution  and  crystallizing. 

Of  this  Compound  take  75  grains  )  {iar\ 

To  each  ounce  of  Water  employed  in  the  bath.  ) 

The  paper  is  floated  in  this  bath  for,  say,  3  minutes,  and  is  then 
dried  in  the  dark.     When  required  for  printing,  it  is  placed  under  the 


94  MODERN  HELIOGRAPHIC  PROCESSES. 

negative  a  sufficient  time  to  make  the  lighter  shades  in  the  print  visible, 
the  time  varying,  say,  from  3  to  10  minutes,  under  direct  sunlight. 
The  exposed  portions  of  the  print  will  be  light-brown  upon  a  yellow 
ground.  So  soon  as  this  condition  is  attained,  the  paper  is  taken  from 
beneath  the  negative,  and  soaked  in  pure  water,  say,  for  20  minutes. 
If  the  negative  be  very  intense,  such  as  to  require  10  or  more  minutes 
of  direct  exposure  to  the  sunlight,  the  soaking  should  be  continued 
longer — say  to  about  half  an  hour.  This  is  desirable,  because  it 
facilitates  the  subsequent  developing.  The  excess  of  bichromate  being 
removed,  leaves  the  whites  of  a  faint-yellow  tint.  Where  pure  whites 
are  required,  it  becomes  necessary  to  destroy  all  traces  of  bichromate, 
where  the  light  has  not  acted,  and  which  are  not  easily  removed  by 
soaking.  For  this  purpose  the  print  is  immersed,  for  1  or  2  minutes, 
in  a  solution  of 


Acid  Sulphite  of  Sodium,  ...  1  part.  )  (iaq) 
Water,  99  parts,  i  '  ^ 

To  prepare  the  developer,  I  take  of 


Gallic  Acid,  2  parts.  > 

Ferrous  Sulphate,  3  parts. 

Aluminum  and  Ammonium  Sulphate,  3  parts. 
Sodium  Hyposulphite,  24  parts. 


.  (150). 


The  ferrous  sulphate,  aluminum  and  ammonium  sulphate,  and  sodium 
hyposulphite,  are  each  dried  separately,  until  free  from  water  pf  crystal- 
lization, and  are  then  pulverized,  and  mixed  with  the  gallic  acid.  This 
compound  will  keep,  and  retain  all  its  properties,  if  protected  from 
dampness. 


Of  this  Composition  take  15  grains. 

Water,  1  ounce. 


.  (151). 


To  develop  the  print,  lay  it  in  a  suitable  dish,  and  pour  upon  it 
the  developing  solution,  to  cover  it,  say,  \  inch  in  depth;  or,  if 
several  prints  are  to  be  developed  at  the  same  time,  take  enough  of 
the  solution  to  cover  all  the  prints.  While  they  are  in  the  solution, 
move  them  frequently,  so  as  to  expose  them  equally  to  the  developing 
solution.  When  the  development  of  the  print  is  completed — which  will 
generally  require  about  10  minutes  —  the  excess  of  the  developer,  absorbed 
by  the  paper,  is  removed  by  soaking  the  print,  for  half  an  hour,  in  water 
slightly  acidulated  with  acetic  acid;  after  which,  and  when  dry,  the 
picture  can  be  mounted.  Its  subsequent  treatment  may  be,  substantially, 
that  usually  applied  to  photographic  prints.    The  sodium  hyposulphite 


CHROMIUM  PROCESSES  R.  B.  WEST'S  PATENTS. 


95 


and  alum,  in  the  developer,  exert  a  reducing  action,  which  prevents  the 
ferrous  salt  from  becoming  oxidized  readily  when  in  solution  and 
exposed  to  the  air,  and  enables  the  bath  to  be  used  repeatedly  for  sev- 
eral days,  if,  after  use,  the  precaution  is  taken  of  putting  it  in  a  tightly- 
corked  bottle,  which  should  be  filled  by  the  solution. 

Any  color,  from  black  to  brown,  can  be  obtained,  after  soaking  out 
the  developer,  by  immersing  the  print,  from  1  to  5  minutes,  in  a  bath 
composed  of 

Sensitizing  Bath,  1  part.  ) 

Water,   2  parts.  ) 

the  time  of  contact  with  the  bichromate  determining  the  shade,  and, 
after  such  treatment,  soak  in  water,  until  the  yellow  tint  is  entirely 
removed. 

If  desired  to  change  the  color  of  a  print  to  reddish-brown,  subject  it, 
after  development,  to  a  bath  composed  of 

Carbonate  of  Soda,  1  ounce.  )  /iko\ 

Water,  1  quart.  ) 

and  dry  immediately. 

In  case  it  be  necessary  to  bleach  the  picture,  it  should  be  done 
after  development,  and  before  any  change  of  color  is  effected,  and  may 
be  well  done  by  subjecting  the  print  to  a  solution  of 


Citrate  of  Ammonia,  1  part. 

Water,  20  parts. 


(154). 


The  paper  may  be  prepared  for  sensitizing  by  any  of  the  known 
processes;  but  I  find  a  very  good  result  is  obtained  from  the  follow- 
ing treatment :  Take  paper  of  a  good  quality,  coat  it  with  a  mixture 
composed  of 


Starch,  .    .    ,  7  parts.  ^ 

White  Sugar,  2  parts. 

Glycerine,   2  parts. 

Boiling  Water,   ......     200  parts. 

Solution  of  pure  Caustic  Potash,      £  part. 


(155). 


or  sufficient  to  Gause  the  coating  to  dry  with  an  even  surface.  The  first 
three  ingredients  are  mixed  with  a  little  cold  water,  and  then  stirred 
into  the  boiling  water.  The  coating  is  applied  by  floating  the  paper 
upon  the  mixture,  in  the  manner  usually  employed  in  the  application 
of  albumen  to  paper.    After  drying,  the  paper  is  dipped  in  a  solution  of 


96 


MODERN  HELIOGRAPHIC  PROCESSES. 


Acetic  Acid, 
Water,    .  . 

and,  when  again  dried,  it  is  ready  for  rise.  In  cases  where  the  intensity 
and  appearance  of  the  print  are  of  little  importance,  paper  may  be  used 
without  this  treatment.  Albumen  paper  does  not,  under  my  improved 
process,  produce  so  good  results,  chiefly  on  account  of  its  density. 

From  my  experiments,  I  believe  the  proportions  for  the  sensitizing 
and  developing  baths  above  given  produce  the  best  results;  but  these 
proportions  may  be  varied,  to  some  extent,  without  departing  from  my 
invention. 

By  this  process,  I  am  enabled  to  produce  photographic  prints  fully 
equal  to  those  produced  by  the  employment  of  silver;  and  it  will  be 
evident,  to  those  skilled  in  this  art,  that  the  cost  of  the  production  is 
very  much  less  than*by  the  usual  process  employing  nitrate  of  silver. 
The  printing  is  also  more  rapid  than  by  the  usual  process,  and  colors 
may  be  more  readily  applied  to  the  print  than  when  the  print  is  pre- 
pared under  the  usual  process. 


2  parts. 
98  parts. 


(156). 


Abridgment  of  U.  S.  Patent  No.  341,083,  dated  May  4,  1886. 

This  invention  relates  to  an  improvement  in  the  preparation  of 
paper  for  printing  photographs,  the  paper  being  specially  adapted  to 
photographic  printing  under  the  process  for  which  Letters  Patent  No. 
273,206  were  granted  to  me  February  27,  1883,  parts  of  the  invention, 
however,  being  applicable  to  other  processes  of  printing ;  and  the  inven- 
tion consists  in  coating  both  sides  of  the  paper  with  a  preparation  of 
starch.  The  paper  best  adapted  is  that  known  in  the  market  as  "  B. 
F.  K.  Rives,  No.  74." 

The  bath,  in  which  the  paper  is  to  be  coated,  is  prepared  after  the 
following  formula : 

Potato  Starch,  6  ounces. 

Glycerine,   2  ounces. 

Sodium  Citrate  (nearly, but  not  quite,  neutral),    £  ounce. 
Pure  Water,   220  ounces. 

To  prepare  the  bath,  take,  say,  TV  of  the  water,  boil  it,  to  expel 
the  air,  then  cool.  In  this,  mix  the  starch,  glycerine,  and  citrate. 
Heat  the  remainder  of  the  water  until  it  boils;  then  remove  from  the 
fire,  and  immediately  add  the  ingredients  previously  mixed  with  the  first 
portion  of  water. 

After  the  one  surface  has  been  thus  presented  to  the  bath,  and  com- 
pletely coated,  the  sheet  is  at  once  removed,  and  inverted,  presenting 
the  other  side,  which  is  allowed  to  float,  for  a  few  seconds,  on  the 


CHROMIUM  PROCESSES  R.  B.  WEST'S  PATENTS. 


97 


surface,  and  then  the  paper  is  suspended  and  dried ;  and,  for  the  best 
results,  the  drying  should  be  rapid. 

The  starch  coating  has  a  strong  adhesive  quality,  and  attaches  the 
paper  permanently  to  the  card.  The  glycerine  makes  the  paper  more 
flexible  when  dry  than  it  otherwise  would  be.  The  sodium  citrate 
makes  the  starch  more  homogeneous,  and  improves  the  whites  of  the 
pictures. 

Abridgment  of  U.  S.  Patent  No.  345,753,  dated  July  20,  1886. 

1.  To  Sensitize  the  Paper. — To  produce  the  best  results,  the  paper 
is  first  coated,  upon  both  sides,  with  a  starch  solution.  The  sensitizing 
solution  is  prepared  from  the  following  formula : 

Potassium  Bichromate,  8  parts.  \ 

Mercuric  Chloride,  4  parts.  >  .  (158). 

Aluminum  Sulphate,  1  part.  ) 

For  convenience,  these  may  be  in  powder.  For  the  bath,  take  pure 
water,  according  to  the  size  of  the  bath,  and,  to  each  ounce  of  water, 
add  50  grains  of  the  above-mentioned  compound,  and  thoroughly  dis- 
solve the  same  in  the  water.  The  paper  is  immersed  in  the  bath,  so 
as  to  wet  both  sides,  not  to  exceed  1  minute.  The  paper  is  dried  — 
may  be  by  artificial  heat,  but  coal-gas,  or  kindred  vapors,  should  be 
avoided,  as  injurious  to  the  surface  —  and  the  paper  thus  sensitized 
should  be  used  the  same  day,  to  produce  the  best  results;  but  it  may 
be  kept  several  days,  in  a  dark,  cool,  damp  place.  The  1  part  of  alumi- 
num sulphate  may  be  omitted,  if  less  contrast  is  desired,  without 
materially  affecting  the  result. 

2.  Printing.  —  The  printing  should  be  carefully  watched,  during  its 
progress,  and  should  be  carried  only  so  far  as  to  make  visible  all  that 
is  desired  to  show  in  the  finished  print.  When  a  sufficient  number  of 
prints  have  accumulated,  they  must  be  washed,  for  20  or  30  minutes,  in 
clear  water,  and  then  developed. 

3.  Developing.  —  The  compound,  from  which  the  developing  bath  is 
made,  is  from  the  following  formula : 

Gallic  Acid,   15  parts.  > 

Pyrogallol,  1  part. 

Ferrous  Sulphate,  15  parts. 

Sodium  Hyposulphite  (dried),  100  parts. 

Aluminum  and  Ammonium  Sulphate  (dried),  15  parts. 
Potassium  Bitartrate,  12  parts.  v 


>  (159). 


These  should  be  kept  in  stock,  dried.  Each  of  the  ingredients 
required  dried,  is  obtained  so  by  fusing  the  commercial  article,  and 


98 


MODERN  HELIOGRAPHIC  PROCESSES. 


maintaining  it  in  that  condition  until  the  water  of  crystallization  is 
driven  off.  This  process  of  drying  is  necessary,  to  prevent  decomposition 
of  the  compound.  If  possible,  the  ingredients  should  be  in  a  fine, 
granulated  condition,  rather  than  in  powder.  The  proportions  called 
for  above  are  weighed  out  after  the  materials  have  been  dried.  When 
mixed,  they  should  be  immediately  packed  in  tight  dry  bottles.  The 
compound  will  then  keep  indefinitely. 

To  prepare  the  developing  bath,  it  should  be  made  the  same  day 
that  it  is  required  for  use.  Add  10  grains  of  the  dried  composition  to 
each  ounce  of  water. 

The  test  of  the  good  working  quality  of  the  ingredients  may  be 
made  as  follows :  After  the  solution  has  stood  for  20  minutes,  it  should 
not  indicate  an  inky  appearance,  or  any  trace  of  it,  but,  on  the  con- 
trary, should  remain  colorless  for,  at  least,  24  hours.  The  print  should 
be  developed  in  from  5  to  10  minutes,  but  prolonged  immersion  should 
not  reduce  the  intensity  of  the  print.  If  it  is  so  reduced,  an  excess 
of  acid  is  indicated.  If  the  development  of  a  cabinet  print  (6^-"X4f"), 
in  2  fluid  ounces  of  bath,  should  produce  an  inky  appearance  of  the 
bath,  or  trace  of  it,  it  would  indicate  an  excess  of  alkali  in  the  bath, 
which  should  be  corrected.  2  fluid  ounces  of  the  bath  is  an  ample 
allowance  for  each  cabinet  print  to  be  developed.  Several  prints  may 
be  developed  in  succession,  if  the  bath  is  allowed  to  repose  some 
minutes  between  the  development  of  each  print.  During  the  developing 
operation,  the  bath  should  be  rocked,  but  in  no  case  should  the  bath 
be  crowded. 

The  method  of  developing  is  as  follows :  After  the  prints  have  been 
washed,  for  20  or  30  minutes,  they  are  placed  in  the  developing  bath, 
until  their  color  changes  from  yellow,  or  light-brown,  to  violet-black. 
The  development  is  completed  when,  on  holding  the  print  up  to  the 
light,  no  brown  tint  is  seen  in  the  shadows.  When  it  has  arrived  at 
this  condition,  a  prolonged  immersion  in  the  developer  will  produce  no 
change,  either  in  the  shadows  or  high-lights.  If,  however,  the  print  has 
become  bronzed  by  prolonged  exposure,  it  will  not  perfectly  develop. 
To  prevent  this  bronzing  —  which  occurs  from  a  thick  nagative  —  the 
clearer  portions  should  be  deadened,  either  by  an  application  to  the 
back,  or  by  roughening  the  varnish  with  retouching-powder. 

4.  Bleaching.  —  After  the  print  has  been  taken  from  the  developing 
bath,  it  should  be  thoroughly  rinsed  in  pure  water ;  but  the  whites  will 
not  be  sufficiently  pure  without  more  or  less  bleaching.  For  this 
purpose,  a  bath,  from  the  following  formula,  is  prepared : 


Bromine,  1  ounce.  \ 

Bromide  of  Potassium,  .  .  2  ounces.  >  .  (160). 
Water,   10  ounces.  ) 


CHROMIUM  PROCESSES  —  R.  B.  WEST'S  PATENTS. 


99 


This  should  be  kept  from  the  light.  When  it  is  required  to  bleach 
the  whites  of  prints,  add  enough  of  the  bleaching  solution  to  water  to 
color  light-yellow  or  amber;  then  immerse  the  prints,  until  sufficiently 
whitened.  If  the  shadows  are  too  dark,  add  a  little  acetic  acid  to  the 
bath.  A  deep  bath  will  produce  better  results  than  a  shallow  one.  As 
soon  as  the  prints  are  bleached,  they  may  be  at  once  mounted,  if  the 
color  is  satisfactory;  if  not,  they  may  be  transferred  to  the  toning  bath. 

5.  Toning.  —  I  employ  the  following  formula,  for  the  preparation  of 
the  compound  for  the  toning  bath,  and  which  may  be  kept  in  stock : 

Potassium  Nitrite,  ....  4  parts.  ) 
Lead  Nitrate,   1  part.  ) 

The  potassium  nitrite  may  be  prepared  from  potassium  nitrate,  or 
saltpetre,  by  melting  in  a  crucible,  and  keeping  at  a  red  heat,  for  2 
hours.  For  the  toning  bath,  for  each  ounce  of  water,  add  5  grains  of 
the  toning  compound.  The  prints  are  immersed  in  this  bath  after 
bleaching.  When  acetic  acid  has  been  added  to  the  bleaching  bath,  it 
is  better  to  wash  the  prints  before  toning.  This  toning,  it  will  be 
observed,  is  the  reverse  of  silver  toning.  If  a  cold -gray  and  black  are 
desired,  a  trace  of  mercuric  chloride,  added  to  the  bath,  will  produce 
that  result.  A  larger  proportion  of  the  mercuric  chloride  will  produce 
a  greenish-black. 


Abridgment  of  U.  S.  Patent  No.  345,938,  dated  July  20,  1886. 

This  invention  relates  to  an  improvement  in  the  process  of  photo- 
graphic printing,  described  in  another  application,  Serial  No.  167,289. 
In  that  application,  the  paper  is  sensitized  by  subjection  to  a  bath,  con- 
sisting of  a  solution,  in  water,  of  potassium  bichromate  and  mercuric 
chloride.  After  the  paper  has  been  properly  dried,  it  is  printed  upon, 
by  exposure  to  light,  under  a  negative,  in  the  usual  manner.  The  photo- 
graphic prints  thus  produced  are  of  a  yellow  color,  which,  not  always 
being  desirable,  the  object  of  my  present  invention  is  to  change  this 
yellow  tint  to  a  more  desirable  violet-black ;  and  the  invention  consists 
in  the  treatment  of  the  prints,  as  hereinafter  described,  and  particularly 
recited  in  the  claims.  After  washing  the  prints,  in  clear  water,  I  subject 
them  to  a  developing  bath,  produced  by  a  solution  of  the  following 
compound,  in  water.    The  developing  compound  consists  of 

Pyrogallol,  2  parts.  > 

Gallic  Acid,  8  parts. 

Ferrous  Sulphate  (dried),  or  other  >  .  (162). 

Ferrous  Salt  soluble  in  water,  10  parts. 

Sodium  Hyposulphite  (dried),    .    .  80  parts,  j 


100 


MODERN    HELIOGRAPHIC  PROCESSES. 


This  compound  is  prepared  in  mass,  and  sold  for  use  when  required. 
The  solution  is  made  by  dissolving  the  compound,  in  water,  in  the 
proportion  of  2  per  cent,  of  the  compound  to  the  water.  By  employing 
the  pyrogallol  in  the  solution,  I  am  enabled  to  change  the  color,  which 
it  produces,  to  a  brown,  or  any  intermediate  shade,  by  subjecting  the 
prints  to  a  toning  bath  containing  lead  nitrite.  Without  the  pyrogallol, 
a  violet-black  is  produced  by  an  aqueous  solution  of  the  three  other  ingre- 
dients; but  the  color  is  not  subject  to  change  in  the  toning  bath.  The 
ferrous  salt  referred  to  is,  preferably,  ferrous  sulphate ;  but  I  sometimes 
use  ferrous  tartrate,  or  other  ferrous  salt,  or  produce  these  salts  in  the 
bath  by  adding  to  the  compound  an  alkaline  tartrate,  etc. 

The  advantage  in  substituting  other  iron  salts  for  the  sulphate  is, 
that  by  so  doing,  I  can  vary  the  color  developed — within  certain  limits  — 
according  to  the  ferrous  salt  used  and  the  proportion  of  pyrogallol, 
from  the  violet-black,  produced  by  the  sulphate  alone,  to  a  warmer  tone, 
using  the  toning  bath  only  when  it  is  necessary  to  obtain  well-marked 
browns. 

In  my  previous  processes,  I  added  alum  to  the  gallic  acid,  ferrous 
sulphate,  and  sodium  hyposulphite,  for  the  purpose  of  obtaining  prints 
having  clear  whites;  but  I  find  this  addition  unnecessary  with  the 
method  of  bleaching  which  I  now  use,  and  objectionable,  as  it  prevents 
the  development  of  a  good  color.  The  print  should  be  left  in  the 
developing  bath  from  5  to  10  minutes,  then  removed  from  the  bath, 
then  washed  in  clear  water,  and  then  may  be  bleached  by  the  action 
of  a  dilute  solution  of  chlorine  or  bromine.  The  bleaching  action  of 
the  halogens  should  be  modified  by  the  presence  of  an  acid,  as  it  is 
then  more  even. 

The  chlorine  bath  is  best  prepared  by  dissolving  1  part  of  calcium 
hypochlorite  in  300  parts  of  water,  and  adding  about  2  parts  of  an 
acid  —  preferably  phosphoric. 

After  the  prints  have  been  bleached,  they  may  be  mounted  in  the 
usual  manner;  or,  if  a  brown  color  is  desirable,  they  are  toned  by  sub- 
jecting them  to  a  bath  consisting  of 

A  1  or  2  per  cent.  Solution  of  Lead  Nitrite,  or  a  Mixture  )  (-iao\ 
of  Potassium,  or  Sodium  Nitrite,  and  Lead  Nitrite.  S 

but,  should  a  cold-gray  be  preferred  to  the  brown,  then  add,  to  the 
toning  bath,  from  2  to  5  per  cent,  of  mercuric  chloride.  The  prints  are 
then  washed  in  clear  water. 

The  proportions  which  I  have  mentioned,  for  the  ingredients  in  the 
several  compounds  and  baths,  are  such  as,  in  practice,  have  produced 
the  best  results;  but  they  may  be  varied  somewhat,  without  departing 
from  my  invention. 

I  would  state  that,  in  order  to  attain  the  best  results,  the  paper 


CHROMIUM  PRINTS  HALLEUR's  PROCESS. 


101 


should  possess  a  considerable  degree  of  porosity,  and  be  thickly  coated 
with  starch,  on  both  sides,  and  the  paper  should  be  free  from  alkaline 
particles. 

2.   Processes  in  which  the  Unaltered  Chromate  Forms  the  Base 
of  the  Picture.  —  Direct  Processes. 

Halleur's  Chromate  of  Silver  Prints.  —  Paper  is  sensitized,  by 
means  of  a  brush,  with  a  mixture  of  equal  volumes  of 

A  Saturated  Solution  of  Bichromate  of  Potassium,  j  (164) 
A  Saturated  Solution  of  Sulphate  of  Copper.  ) 

and  may  be  used  as  soon  as  dry,  or  preserved,  for  some  time,  in  a  dark 
place.  By  exposure  to  light,  under  a  drawing,  or  other  positive,  the 
uncovered  parts  will,  at  first,  become  brown,  and  the  picture  will 
appear  as  a  negative.  On  continued  exposure,  the  brown  color  becomes 
lighter,  and  the  picture  will  then  be  positive.  The  exposure,  through 
tracing  paper,  and  in  the  direct  rays  of  the  sun,  requires  from  25  to  30 
minutes.  The  prints  are  developed  and  toned  with  a  solution  of  nitrate 
of  silver,  of  any  strength.    We  have  used  a  solution  of 


and  applied  the  same  by  means  of  a  camel's-hair  brush.  The  beautiful 
blood-red  picture,  which  appears  at  once,  will  be  fixed  by  washing  it  in 
pure  water.  If  the  water  contains  a  chloride,  or  if  a  small  amount  of 
sodium  chloride  (common  salt)  be  dissolved  in  the  water,  the  picture 
disappears  entirely;  but  it  remains  latent  in  the  paper,  and  can  be 
re-developed  by  exposing  it,  still  wet,  to  the  direct  rays  of  the  sun,  and 
then  drying  it.  The  color  of  the  picture  will,  however,  change  hereby. 
According  to  the  quantity  of  salt  used,  it  will  vary  from  a  rose-color 
to  a  dark-violet.  The  longer  it  is  left  in  the  sun,  the  more  the  print 
will  gain  in  beauty. 

According  to  other  operators,  the  sensitizing  solution,  for  this  process, 
is  composed  of 


Nitrate  of  Silver. 
Distilled  Water, 


20  grains  troy. 
1  fluid  ounce. 


•  j   .  (165). 


Bichromate  of  Potash. 
Sulphate  of  Copper,  . 
Distilled  Water,     .  . 


10  grains.  ) 

20  grains,  i  .  (166). 


1  ounce. 


The  author  had  made  over  1,000  prints  by  this  process,  which 
looked  very  beautiful,  but,  in  about  6  months,  nearly  all  were  spoiled, 
as  the  ground  became  green,  and  the  picture  faded  away. 


102 


MODERN  HELIOGRAPHIC  PROCESSES. 


Cros  and  Vergerand's  Chromate  of  Silver  Process.  —  Suitable 
paper  is  coated  with  the  following  solution : 

Bichromate  of  Ammonia,      .    .    2  parts.  \ 

Glucose  (Grape-Sugar),    ...  15  parts.  >     .  (167). 

Water,  100  parts.  ) 

When  dry,  it  is  exposed  to  light,  under  a  drawing,  or  other  positive. 
As  soon  as  the  yellow  paper  becomes  gray,  it  is  removed,  and  immersed 
in  a  bath  of 

Nitrate  of  Silver,  1  part,  j 

Water,  100  parts.  V   .    .  (168). 

Acetic  Acid,    .......  10  parts.  ) 

The  image  will  immediately  appear,  of  a  ruby  hue,  due  to  the  bichro- 
mate of  silver  formed.  The  print,  on  being  washed,  retains  the  red 
impression  of  the  insoluble  bichromate,  which  becomes  dark-brown  on 
exposure  to  sunlight.  On  submitting  the  print,  when  dry,  to  the  fumes 
of  sulphureted  hydrogen,  or  dipping  it  in  a  solution  of  sulphite  of 
copper  and  potash,  it  becomes  black. 


Foxtype.  —  This  process  has  been  patented  in  Great  Britain,  by  its 
discoverer,  Thomas  Fox,  Esq. 

Sensitizing  Solution. 

Bichromate  of  Potassium,     .    .    1  part.  \ 

Sulphate  of  Copper,     .    .    .    .    2  parts.  >  .    .  (169). 

Water,  32  parts.  ) 

Ordinary  writing  or  drawing  paper  is  floated  upon  this  solution,  for 
4  or  5  minutes,  and  then  hung  up  to  dry,  in  the  dark.  When  dry,  the 
paper  is  submitted,  under  a  drawing,  or  transparent  positive,  to  the 
action  of  light.  The  time  of  exposure  is — in  the  sun  —  about  2  or  3 
minutes. 

Development.  —  Shavings  of  logwood  are  boiled  in  water,  for  about 
2  hours;  the  decoction  is  then  filtered,  and  used  hot.  The  prints  are 
floated  upon  the  developer  until  they  are  sufficiently  intense.  They  are 
then  immersed  in  a  hot  solution  of  alum,  in  order  to  remove  the 
yellow  color  from  those  parts  of  the  paper  on  which  the  light  has  acted. 
Finally,  the  prints  are  washed  well,  dried,  and  varnished. 

Different  shades  of  color — from  blue,  purple,  light-black,  and  deep- 
black —  can  be  obtained  by  varying  the  strength  of  the  sensitizing  solu- 
tion, as  also  the  decoction  of  logwood. 


Willis's  aniline  process. 


103 


Willis's  Aniline  Process. — This  process  is  extremely  useful  for 
copying  plans  and  other  simple  line-drawings.  It  was  originally 
invented  and  patented  by  Mr.  Wm.  Willis,  and,  later,  developed  and 
improved  by  other  investigators.  Dr.  Vogel  has  made  the  most  exten- 
sive experiments,  in  regard  to  the  aniline  process,  and  published  the 
results  of  the  same.  The  Willis  patent  has  expired,  and  it  is  to  be 
hoped  that  this  process  will  now  be  more  extensively  used. 

The  aniline  process  is  founded  upon  the  property  of  the  bichromates 
of  forming,  with  aniline  salts,  dark-colored  precipitates.  The  lower  oxides 
of  chromium,  which  are  produced  by  light  on  paper  that  has  been 
coated  with  a  solution  of  bichromate  of  potash,  also  re-act  upon  aniline 
salts,  but,  comparatively,  only  very  slightly. 

Dr.  Vogel  says,  not  every  kind  of  paper  is  equally  suitable  for 
aniline  prints.  Rives'  paper  gives,  for  example,  but  imperfect  results. 
On  Steinbach's  paper,  he  obtained  the  best  prints. 

The  best  sensitizing  solution  is,  according  to  Vogel,  composed  of 

Bichromate  of  Potassium,    ...    1  part.  \ 

Phosphoric  Acid,  of  1.126  spec,  wt,  10  parts.  >     .    .  (170). 

Water,  10  parts.  ) 

The  intensity  of  the  color  of  the  finished  prints  increases  with  the 
quantity  of  the  chromate  —  and  more  so  with  the  quantity  of  the  phos- 
phoric acid — which  the  sensitizing  solution  contains.  The  sensibility 
decreases  as  the  quantity  of  the  acid  increases. 

Dawson  gives  the  following  recipe  for  the  sensitizing  solution : 

Bichromate  of  Potassium,  .  30  grains.  \ 

Phosphoric  Acid  (diluted),  .    1  fluid  ounce.  >    .    .  (171). 

Water,  1  fluid  ounce.  ) 

According  to  Reynold,  the  sensitizing  solution  is  composed  of 

Concentrated  Solution  of  Bichromate  \ 

of  Potassium,  (1  to  10),  4   fluid  ounces.  >    .    .  (172). 
Sulphuric  Acid,      ....  1^-  fluid  ounces.  ) 

Dr.  Vogel  did  not  succeed  with  Reynold's  solution.  The  surface  of 
the  paper  was  tinted  disagreeably  grayish-brown,  and  the  print  was 
weak,  and  appeared  to  be  sunk  into  the  paper. 

The  sensitizing  is  best  done  by  floating  the  paper  upon  the  solution, 
for  about  1  minute  (not  longer),  and  then  drying  it  quickly,  in  a  warm 
and  dark  room,  or  near  a  stove.  If  the  paper  is  floated  too  long,  the 
solution  penetrates  into  the  paper,  and  the  back  will  be  colored. 


104 


MODERN  HELIOGRAPHIC  PROCESSES. 


The  correct  time  of  exposure  to  light  is  of  great  importance  in  this 
process.  If  the  exposure  was  too  short,  the  ground  of  the  finished 
prints  will  also  be  colored;  if  it  was  continued  too  long,  the  picture 
will  either  not  develop  at  all,  or  it  will  come  out  but  partly,  or  very 
slowly. 

The  time  of  exposure  to  diffused  light  required  is,  for  originals, 

On  tracing  paper,    .    .    .    about  10  minutes. 

On  thin  drawing  paper,   .    about    1  hour. 

On  thick  drawing  paper,  .    about    2  to  3  hours. 

In  the  direct  rays  of  the  sun,  the  exposure  required  is  only  -J-  of  the 
time  given.  In  order  to  determine,  with  certainty,  whether  a  print  has 
been  exposed  sufficiently  long,  it  is  advisable  to  expose,  with  the  main 
printing  frame,  narrow  strips  of  the  same  sensitized  paper,  under  a  small 
glass  plate,  and  under  similar  paper  to  that  on  which  the  original  is 
made,  in  the  manner  recommended  and  described  on  page  70,  in  the 
article  on  direct  cyanotypy. 

The  developing  is  done  in  a  shallow  box,  the  size  of  the  largest 
print.  To  the  inner  side  of  the  lid  of  the  fuming  box,  a  few  sheets  of 
blotting  paper  must  be  fastened,  which  are  to  be  sprinkled,  uniformly, 
with  a  solution  of 

Raw  Oil  of  Aniline,   .    .    .  20  to  40  drops.  )  (173) 
Benzole,    .  1  ounce.  ) 

The  print  is  placed  upon  the  bottom  of  the  box.  The  more  aniline 
the  solution  contains,  the  quicker  the  developing  process  goes  on.  If 
the  print  was  not  over-exposed,  the  image  appears  in  a  few  minutes, 
and  gains  continually  in  intensity.  The  color  is  a  dirty  blue-green- 
black,  which  becomes  a  fine  blue  when  the  print  is  immersed  in  water. 
By  continuing  the  fuming  process  sufficiently  long,  a  dark  bluish-black 
color  may  be  obtained. 

The  duration  of  the  fuming  process  depends  upon  the  time  the  print 
was  exposed  to  the  action  of  light.  Under-exposed  prints  ought  not  to 
be  fumed  as  long  as  is  required  to  obtain  dark-blue  or  bluish-black 
pictures,  because  the  ground  would  also  become  tinted.  Sometimes  it 
happens  that  the  prints  become  of  a  green  color  in  the  washing  water ; 
this  can  be  easily  converted  into  blue,  by  adding  a  little  ammonia  to 
the  washing  water.    Acid  produces  a  green,  alkalies  a  blue,  color. 

The  washing  of  the  prints  in  acidified  water  has  the  advantage  of 
removing  the  chrome-oxide  from  the  paper.  The  ground  will  become 
nearly  white  when  the  prints,  after  the  first  washing  in  water,  are 
immersed  in  a  bath  of 


Sulphuric  Acid,  ....  1  part.  ) 
Water,  100  parts.  ) 


CHROMIUM  PRINTS  GOTTLIEB'S  PATENT. 


105 


then  washed  once  more  in  pure  water,  and,  finally,  tinted  blue  again,  by 
plunging  them  into  diluted  ammonia  water,  consisting  of 

Ammonia  Water,  ....  1  part.  )  (175) 
Pure  Water,  100  parts.  )    '      1  '  ;' 

If  the  paper  was  sensitized  with  the  solution,  according  to  Dr.  Vogel's 
recipe,  and  if  the  time  of  exposure  was  correct,  the  acid  bath  will  hardly 
be  necessary.  Sometimes  the  prints  will  look  spotted,  when  they  get 
wet  in  the  washing  water,  although  they  were  perfectly  clean  before. 
Such  spots  will  disappear  in  drying. 

The  washing  water  should  often  be  renewed  —  say  eight  times  —  and 
if  the  tone  should  be  green,  a  little  ammonia  may  be  added  to  the 
fourth  water.  The  prints  may  be  toned  a  fine  and  durable  green,  by 
immersing  the  same  in  a  diluted  solution  of  gallic  acid. 


V.  J.  M.  Gottlieb's  Method  op  Reproducing  Drawings  and  Other 

Line-Works  op  Art. 


Abridgment  of  U.  S.  Patent  No.  306,481,  dated  October  14,  1884- 

The  following  solution  is  made  use  of,  in  preparing  the  paper;  the 
materials  employed  being  those  named,  or  substances  having  equivalent 
chemical  properties,  and  in  about  the  proportions  stated : 


Bichromate  of  Potash, 
Vanadate  of  Ammonia,  . 
Chloride  of  Sodium,    .  . 
Sulphuric  Acid  (about  98°). 
Distilled  Water,  .... 


9.6  grams.  > 
0.015  grams. 

,    9.6  grams. 

.  21  grams. 

441  grams. 


>  ■  (176). 


These  substances  are  to  be  carefully  and  thoroughly  mixed  together. 
The  paper  to  be  sensitized  is  coated  over  with  this  solution,  and  then 
allowed  to  dry,  for  a  few  minutes,  in  a  dark  place.  The  reproduction 
is  effected  by  exposure  to  the  sunlight.  After  exposure,  for  the  proper 
length  of  time,  to  the  action  of  light  —  varying,  from  10  seconds  to  15 
minutes,  according  to  the  intensity  of  the  light  and  the  transparency 
of  the  original  drawing  —  the  impression  is  removed,  and  developed  by 
steam  and  aniline  oil.  To  effect  this,  a  few  drops  of  aniline  oil  are 
put  into  the  water,  or  the  steam  allowed  to  pass  through  a  cloth  upon 
which  the  oil  is  placed.  The  exposure  to  the  steam  and  vapor  of  the 
aniline  oil  may  be  in  a  closed  vessel,  or  box,  or  the  paper  may  be 
passed  over  the  vapors  by  hand,  in  the  open  atmosphere,  after  which 
the  reproduction  is  dried  quickly,  and  will  be  found  to  be  a  durable 
picture,  the  lines  being  black,  or  nearly  so,  and  the  surface,  or  back- 
ground, of  a  very  light  greenish  tinge. 


106  MODERN  HELIOGRAPHIC  PROCESSES. 

I  have  sometimes  added  ether,  or  aqua  ammonia,  to  the  solution 
before-named,  for  varying  the  color  of  the  lines,  or  the  background,  or 
for  rendering  the  surface  more  or  less  sensitive  than  that  prepared  by 
the  aforesaid  formula.  The  ammonia  renders  the  operation  more  reli- 
able, so  that  the  lines  are  not  injured  if  the  exposure  is  unnecessarily 
long. 

3.  Processes  which  are  Based  Upon  the  Property  of  a  Film  of 
Gelatine,  Gum,  or  the  like,  Containing  a  Chromate,  to  Become 
Insoluble  by  the  Action  of  Light. 

Abridgment  of  English  Patent  No.  2,815,  of  December  13,  1855,  to  Alphonse 

Louis  Poitevin. 

*  *  *  *  One  or  more  films  of  a  concentrated  solution 
of  albumen,  fibrine,  gum  arabic,  gelatine,  or  similar  organic  substance, 
and  a  concentrated  solution  of  a  chromate  or  bichromate  of  potash,  or 
any  base  which  does  not  precipitate  the  organic  matter  of  the  first 
solution,  are  applied  to  the  paper.  ******* 

Various  liquid  and  solid  colors  are  applied,  upon  paper,  cloth,  glass, 
and  other  surfaces,  by  mixing  such  colors  with  the  aforesaid  mixture 
of  a  chromate  or  bichromate  with  organic  matter,  and  applying  this 
new  mixture,  or  combination,  to  the  paper  or  other  fabric  surface.  The 
photographic  impression  is  produced,  upon  this  prepared  surface,  by  the 
action  of  light  passing  through  a  negative  photographic  picture,  or  an 
engraving,  or  other  suitable  object,  or  screen,  or  in  the  camera  obscura, 
and  it  is  then  washed,  with  a  sponge  and  a  large  quantity  of  water. 
The  albumen,  or  other  organic  matter,  is  rendered  insoluble  at  the 
parts  where  it  has  been  acted  upon  by  light,  and  the  design  is  thus 
produced  in  the  color  which  has  been  employed.  Mixtures  containing 
different  colors  may  be  applied  to  different  parts  of  the  surface,  corres- 
ponding to  different  parts  of  the  negative,  or  screen,  employed  to 
produce  the  photographic  impression. 

M.  Tilhet's  Process  of  Reproducing  Drawings  and  Designs. 
Abridgment  of  U.  S.  Patent  No.  251,746,  dated  January  3, 1882* 

This  invention  has  for  its  object  a  novel  method  of  reproducing 
copies  of  all  kinds  of  drawings,  or  other  designs,  and  it  is  applicable 
to  the  reproduction  of  such  copies  upon  any  kind  of  paper,  and  either 
in  black,  red,  blue,  green,  or  any  other  color. 

In  order  to  put  the  invention  in  operation,  the  paper  upon  which 
the  design  is  to  be  reproduced,  in  order  to  prepare  a  negative  copy,  is 


*  Patented  in  France,  August  21,  1879;  in  England,  November  26,  1880;  in  Belgium, 
November  27,  1880,  and  in  Germany,  November  29,  1880. 


CHROMIUM  PRINTS  M.  TILHET's  PATENT. 


107 


first  passed  through  a  bath,  composed  of  the  following  materials,  in 
about  the  proportions  given  —  that  is  to  say: 


White  Soap,   30  parts,  by  weight.  > 

Alum,   30  parts,  by  weight. 

Flanders  Glue,    ....  40  parts,  by  weight. 

Whites  of  Eggs,  beaten  up,  10  parts,  by  weight. 

Glacial  Acetic  Acid,    .    .  2  parts,  by  weight. 

Alcohol,  at  60°,   ....  10  parts,  by  weight. 

Water,   500  parts,  by  weight.  J 


(177). 


The  paper,  after  leaving  this  bath,  is  then  passed  through  a  second 
bath,  composed  as  follows : 


Burnt  Umber,  ground  in  Alcohol,  50  parts,  by  weight.  " 

Black  Pigment,  20  parts,  by  weight. 

Flanders  Glue,  10  parts,  by  weight. 

Water,    500  parts,  by  weight. 

Bichromate  of  Potash,  ....    10  parts,  by  weight. 


>•  (178). 


The  paper,  having  been  thus  treated,  must  be  kept  in  a  dark  place. 

In  order  to  prepare  positive  paper  for  the  prints,  a  bath  is  used 
similar  to  the  last,  but  without  the  umber,  for  which  black  pigment  is 
substituted ;  or,  to  obtain  colored  proofs  instead  of  black  ones,  the 
black  pigment  is  replaced  by  a  pigment  of  red,  blue,  or  any  other 
desired  color. 

To  prepare  the  copies,  the  design  or  drawing  is  placed  in  an  ordi- 
nary photographic  printing  frame,  the  back  of  the  design  being  next  to 
the  glass,  and  a  sheet  of  negative  paper,  prepared  in  the  way  first 
described,  is  placed  in  contact  with  it.  The  frame  is  then  exposed  to 
light  —  2  minutes'  exposure  being  sufficient  in  good  weather.  The  sensi- 
tive paper  is  then  removed  from  the  frame,  in  a  dark  place,  and  is 
placed  in  water,  when  the  design  becomes  visible,  in  white,  and  the 
paper  is  then  allowed  to  dry. 

In  order  to  obtain  positive  pictures  from  the  negative  thus  prepared, 
the  latter  is  placed  in  the  printing  frame,  with  a  sheet  of  the  positive 
paper  in  contact  with  it,  and,  after  exposure  to  light  for  a  sufficient 
time  —  that  is  to  say,  about  2  minutes — the  positive  paper  is  removed, 
in  a  dark  place,  and  is  plunged  into  water,  which  removes  the  part  of  the 
pigment  which  has  not  been  affected  by  the  light,  without  its  being 
necessary  to  touch  it. 

Any  number  of  copies  of  the  design,  or  drawing,  may  be  produced, 
by  the  novel  method  described,  upon  any  kind  of  paper,  and  in  any 
color  or  colors. 


108 


MODERN  HELIOGRAPHIC  PROCESSES. 


W.  W.  Sherman's  Process  of  Producing  Photographs  in  Permanent 

Pigments. 

Abridgment  of  U.  S.  Patent  No.  332,364,  dated  December  15,  1885. 

I  prepare  2  stock  solutions,  which  I  call  "  No.  1,"  and  "  No.  2," 
respectively,  the  first  being  used  in  the  sizing  of  the  paper,  and  the 
second,  in  connection  with  the  first  —  together  with  pigments  and  a  sen- 
sitizing salt  —  in  preparing  the  paper  for  printing. 

I  prepare  my  stock  solution  No.  1  by 

Soaking  Nelson's  Photographic  Gelatine  No.  1,  in  cold  water,  \ 

for  15  minutes,  pouring  off  the  water  not  taken  up  by  the  >  (179). 
gelatine,  melting  the  residue,  by  the  aid  of  heat,  and  filtering.  ; 

To  size  the  paper,  take  1  part  of  the  stock  solution  No.  1  and  dilute 
with  3  parts  of  water.  The  paper  may  be  floated  on  the  sizing  solution, 
or  drawn  through  it,  or  the  sizing  may  be  applied  by  means  of  a 
brush,  the  object  being  to  evenly  coat  the  surface  to  receive  the  impres- 
sion.   After  sizing,  the  paper  is  allowed  to  dry. 


(180). 


My  stock  solution  No.  2  is  made  by 

Soaking  Coignet's  Gelatine  -J-  hour  in  cold  water,  pouring  off. 
as  before,  the  water  not  taken  up  by  the  gelatine,  and  then 
melting  the  residue,  by  the  aid  of  heat,  adding  to  the 
melted  mass  6  times  its  bulk  of  water,  and  filtering. 

To  prepare  the  paper  for  receiving  the  impression,  I 

Take  \  fluid  ounce  of  each  Stock  Solution  Nos.  1  and  2,  and  add  ^ 
drams  of  a  Saturated  Solution  of  Bichromate  of  Potash, 
and  a  [sufficient  quantity  of  pigment  —  previously  mixed  ?  (181). 
with  water  —  to  produce  results  of  the  desired  depth,  together 
with  enough  water  to  make  the  entire  mixture  2  fluid  ounces. 


This  mixture  is  thrown  on  the  paper  by  means  of  an  atomizer  — 
such  as  is  used  by  physicians  —  operated  by  means  of  a  continuous 
current  of  air  from  a  suitable  air-pump,  or  it  may  be  applied  by  means 
of  the  air-brush;  all  of  which  operations  to  be  performed  in  non- 
actinic  light,  as  well  known.  The  paper  is  ready  for  exposure  as  soon 
as  dry,  which  exposure  is  effected,  in  the  usual  manner,  by  allowing 
the  light  transmitted  through  a  negative  to  fall  on  the  paper.  The  time 
of  exposure  varies  with  the  character  of  the  negative  and  the  intensity 
of  the  light,  but  is  about  ^  of  that  required  by  the  ordinary  silver 


CHROMIUM  PRINTS  NIGROGRAPHIC  PROCESS. 


109 


process,  under  the  same  conditions.  After  exposure,  the  paper  is  im- 
mersed in  water,  of  temperature  from  80°  to  120°  F.,  which,  in  a  few 
minutes,  generally  suffices  to  dissolve  the  gelatine  in  the  unexposed 
parts.  The  paper  is  then  placed  on  a  frame  covered  with  sheeting,  and 
washed  with  a  spray  of  water,  consisting  of  a  number  of  small  jets 
having  sufficient  force  to  dislodge  the  particles  of  pigment  and  gelatine 
from  the  parts  not  acted  upon  by  the  light. 

While  the  solutions  that  I  have  described  are  such  as  I  prefer  to 
use  under  ordinary  circumstances,  these  may  be  varied  somewhat,  at  the 
will  of  the  operator,  under  other  circumstances.  A  sizing  solution  of 
less  solubility  tends  to  produce  results  having  sharper  contrasts;  the 
same  being  true  with  regard  to  the  solutions  with  which  the  pigments 
are  mixed,  and,  in  preparing  the  paper  for  printing,  I  may  substitute  a 
saturated  solution  of  bichromate  of  ammonia  for  that  of  potash,  to 
secure  a  greater  degree  of  sensitiveness,  when  required,  and  in  case  a 
stronger  sizing  solution  is  used  than  that  hereinbefore  described,  it  will 
be  necessary  to  increase  the  time  of  exposure  correspondingly ;  but  the 
constituents  and  proportions  already  named  have  been  found  generally 
satisfactory. 

If  desired,  the  solution  of  bichromate  of  potash,  or  ammonia,  may  be 
omitted  from  the  described  mixture  of  pigment,  water,  and  solutions 
Nos.  1  and  2,  and,  after  this  mixture  has  been  sprayed  upon  the  paper 
and  allowed  to  dry,  the  paper  may  be  sensitized  by  floating  it,  face 
down,  upon  a  solution  of  said  bichromate. 

Ludwig  von  Itterheim's  Nigrographic  Positive  Process.  —  Smooth 
and  well  sized  (glue-sized)  drawing  paper  is  coated,  by  means  of  a  brush, 
in  subdued  light,  with  the  following  solution : 

Gum  Arabic,  .... 

Water,  

Potassium  Bichromate,  . 
Alcohol,  

The  prepared  paper  will  keep  —  if  preserved  in  a  dark  place  —  in  a 
serviceable  condition,  for  a  few  days.  The  exposure  to  diffused  light, 
and  under  a  tracing,  requires  from  5  to  10  minutes.  After  exposure, 
the  prints  are  washed  in  water  until  the  lines  of  the  drawing  appear  to 
be  engraved;  then  they  are  taken  out  of  the  water  and  dried.  When 
perfectly  dry,  the  entire  face  of  the  print  is  thinly  and  uniformly 
coated  with  a  varnish  composed  of 

Strong  Alcohol,  

Shellac,   

Fine,  Impalpable  Lampblack,  . 


25  parts. 
100  parts. 
7  parts. 
1  part. 


(182). 


20  parts.  \ 
1  part.  [  .  (183). 
3  parts.  ) 


110 


MODERN  HELIOGRAPHIC  PROCESSES. 


This  is  best  done  by  means  of  a  sponge,  and  care  must  be  taken 
that  all  the  deepened  lines  are  filled  with  the  black  varnish. 

When  the  black  coating  is  dry,  the  sheets  are  immersed  in  a  dis- 
charging bath,  consisting  of 

Water,  100  parts.  )  (iqa\ 

Sulphuric  Acid,     ....    2-3  parts.  ) 

and  left  therein  until  the  superfluous  black  can  be  removed  by  gentle 
brushing.  The  lines  of  the  drawing  then  appear,  in  black  upon  a  white 
surface,  and  the  copies  thus  obtained  will  have  the  same  appearance 
as  a  good  autograph. 


Carbon  Prints,  According  to  Hattgk  and  Liesegang.  —  Beat  the 
whites  of  several  eggs  to  a  froth,  leave  it  stand  to  settle,  pour  off  the 
liquid  part,  and  dilute  this  with  an  equal  volume  of  water ;  then  color 
the  diluted  albumen  with  liquid  india-ink.  Instead  of  the  albumen,  a 
solution  of  gum  arabic,  in  water,  may  be  used. 

With  the  black  liquid,  thin  white  paper  is  coated  as  uniformly  as 
possible,  by  means  of  a  wide,  soft  brush.  When  dry,  this  paper  may  be 
preserved  for  a  long  time. 

Shortly  before  use,  the  paper  is  sensitized  by  a  solution  of 

Bichromate  of  Potassium,     .    .    1  part.  ) 
Water,  10  parts.  )  * 


which  is  to  be  applied  very  freely,  to  the  back  of  the  paper,  with  a 
brush.  After  a  few  minutes,  the  solution  is  equalized,  with  the  nearly 
dry  brush.  The  sensitizing  may  be  done  in  subdued  daylight,  but  the 
drying  of  the  paper  must  take  place  in  the  dark. 

The  paper  is  to  be  placed,  in  the  printing  frame,  so  that  the  black 
albumen  side  comes  in  contact  with  the  original.  The  exposure  to 
light  is  to  be  continued  until  the  lines  of  the  drawing  are  plainly 
visible  on  the  yellow  back  of  the  paper.  After  the  print  has  been  taken 
out  of  the  printing  frame,  it  is  plunged  into  water,  for  a  minute,  and  then 
laid  on  a  smooth,  clean  board,  or  on  a  plate  of  glass.  Then  the  image 
is  developed,  under  a  hydrant,  and  by  means  of  a  soft  brush,  until  all 
adherent  particles  of  the  film  on  which  the  light  did  not  act  are 
removed.  After  this,  the  print  is  put  in  clean  water  again,  in  order 
to  remove  all  the  soluble  chromium  salt  from  the  paper,  and,  finally,  it  is 
hung  up  to  dry.  It  is  evident  that,  by  this  process,  a  negative  print 
will  be  received  from  a  positive  original,  but  such  a  negative  may  be  used 
for  making  positives,  either  by  the  same  process  or  by  another. 


CHROMIUM  PROCESSES  CARBON  PRINTS. 


Ill 


Carbon  Prints,  According  to  the  Author.  —  A  saturated  Stock 
Solution  of  potassium  bichromate  —  which  requires  about 

Potassium  Bichromate,     ...    1  part.  )  (igQ) 
Water,  10  parts.  S 

is  filtered;  then  ammonia  water  is  continually  added  to  the  solution, 
until  the  reddish  color  of  the  latter  commences  to  turn  yellow.  In  a 
dark  place,  this  solution  remains  in  a  serviceable  condition  for  a  long 
time. 

Sensitizing  Solution. 

Of  the  above  Stock  Solution,  4  ounces. 
Gum  Arabic  (powdered),  .  .  -J  ounce. 
White  Granulated  Sugar,  .  .  T3g-  ounce. 
Lampblack,  ounce. 

The  lampblack  is  ground,  with  a  little  glycerine  and  alcohol,  by 
means  of  a  spatula,  or  a  knife,  on  a  porcelain  plate,  so  as  to  form  a 
stiff  paste,  and  then  mixed  with  the  other  ingredients.  The  solution 
must  be  continually  stirred  or  shaken,  as  the  lampblack  has  a  tendency 
to  settle  at  the  bottom  of  the  bottle. 

After  the  gum  and  the  sugar  have  dissolved,  the  solution  is  applied 
to  the  paper,  by  means  of  a  bristle  brush,  in  parallel  strokes.  This 
must  be  done  very  quickly  and  uniformly.  Then  the  coating  is  equal- 
ized, by  passing  over  the  paper,  with  the  brush,  in  a  direction  rectangular 
to  the  first  strokes. 

The  dry  paper  should  have  a  medium  olive-green  color. 

When  the  paper  is  put  into  the  printing  frame,  it  must  be  perfectly 
dry;  otherwise  the  negative,  or  original,  would  stick  to  it. 

Success  depends,  a  great  deal,  upon  the  correct  time  of  exposure. 
If  the  original  is  on  tracing  paper,  or  tracing  cloth,  the  exposure,  in 
the  sun,  requires  from  8  to  10  minutes.  The  picture  will  be  visible  in 
transmitted  light,  and,  from  the  strength  of  it,  we  may  easily  judge 
whether  the  light  has  acted  for  a  sufficient  length  of  time. 

When  the  print  is  taken  out  of  the  printing  frame,  it  is  soaked  in 
water,  until  the  parts  of  the  film  on  which  the  light  did  not  act  become 
so  soft  that  they  can  easily  be  removed  by  means  of  a  camel's-hair 
brush.  As  soon  as  the  picture  is  completely  developed,  the  print  is 
drawn,  a  few  times,  through  clean  water,  and  then  hung  up  to  dry. 

If  the  exposure  was  insufficient,  the  image  will  appear  very  quickly ; 
but,  before  the  white  parts  are  pure,  parts  of  the  picture  will  be  taken 
away  by  the  brush  in  developing.  If  the  print  was  over-exposed,  the 
picture  appears  very  slowly,  and  it  is  impossible  to  remove  the  coating 


112 


MODERN   HELIOGRAPHIC  PROCESSES. 


entirely  in  some  places  which  should  be  white.  Sometimes  such  prints 
may  be  saved  by  using  warm  water  for  developing. 

The  quantum  of  sensitizing  solution  given  above  is  sufficient  for 
covering  32  square  feet  of  paper. 

4.  Processes  which  are  Based  Upon  the  Property  of  Bichromated 
Gelatine,  Albumen,  etc.,  to  Receive  Fatty  Printing  Ink  in 
Places  upon  which  Light  was  Allowed  to  Act,  while  Those 
Parts  Untouched  by  Light  Imbibe  Water. 

Abridgment  of  English  Patent  No.  2,815,  of  December  13,  1855,  to  Alphonse 

Louis  Poitevin. 

One  or  more  films  of  a  concentrated  solution  of  albumen,  fibrine,  gum 
arabic,  gelatine,  or  similar  organic  substance,  and  a  concentrated  solu- 
tion of  a  chromate — or  bichromate  —  of  potash,  or  any  base  which  does 
not  precipitate  the  organic  matter  of  the  first  solution,  are  applied  to 
the  paper,  stone,  metal,  glass,  wood,  etc.,  which  is  to  receive  the  design. 
If  the  impression  is  to  be  taken  by  contact,  the  film  is  then  dried ;  if 
in  the  camera,  it  may  be  used  moist.  After  a  sufficient  exposure,  if  the 
surface  has  become  dry,  or  has  been  used  in  a  dry  state,  it  is  moist- 
ened with  water,  by  means  of  a  sponge,  and,  while  moist,  the  greasy 
ink  or  matter  is  applied  to  the  surface,  to  which  it  will  be  found  to 
adhere  in  those  parts  only  which  have  been  affected  by  the  light.  The 
print  may  be  retained  on  the  surface  on  which  it  is  first  produced,  or 
transferred,  or  printed  upon  paper  or  other  suitable  material,  and  the 
operation  repeated.  A  design  is  thus  obtained  upon  lithographic  stone, 
or  other  suitable  material,  from  which  impressions  may  be  multiplied 
by  the  method  of  lithographic  printing  —  the  moistened  surface  with 
a  greasy  ink. 

Captain  Abney's  Papyrography.  —  Paper  is  floated,  for  2  minutes, 
upon  a  warm  solution  of 

Gelatine,  6  parts.  \ 

Bichromate  of  Potassium,     .    .    3  parts.  >  .  (188). 
Water,  100  parts.  ) 

hung  up  to  dry,  and  floated  again  on  the  same  solution.  The  second 
time,  the  paper  must  be  hung  up  to  dry  in  a  position  opposite  to  the 
first,  so  that  the  edge  which  was  down  the  first  time  will  now  be  up. 
This  will  cause  the  coating  to  be  more  uniform.  The  bichromate  may 
be  omitted  in  the  first  solution,  and  the  paper,  shortly  before  use,  floated 
on  a  solution  of 


CHROMIUM  PRINTS  DUSTING-IN  PROCESS. 


113 


Bichromate  of  Potassium, 
Water,  


3  parts, 
100  parts, 


:-  J  .  (189). 


The  drying  must  take  place  in  the  dark.  After  exposure,  the  print 
is  immersed  in  a  dilute  solution  of  alum,  and,  when  the  greater  part  of 
soluble  chromate  has  dissolved,  placed  upon  a  glass  or  zinc  plate,  and 
superficially  dried  with  blotting  paper.  Then  it  is  inked-in  with  litho- 
graphic ink,  by  means  of  a  soft  leather  or  velvet  hand-roller. 

When  this  has  been  done,  the  print  is  soaked  in  water,  until  all  the 
soluble  chromate  is  removed.  If  the  print  was  exposed  under  a  nega- 
tive, the  drawing  will  be  in  black  lines  upon  a  white  ground;  if  a 
positive  was  used,  in  white  lines  on  a  black  ground. 

From  such  a  print,  40  to  50  good  impressions  may  be  taken,  on  an 
ordinary  printing  press,  or  with  a  wash-wringer,  or  by  laying  a  piece  of 
paper  over  the  inked  print,  on  the  glass  or  zinc  plate,  and  passing  over 
the  same  with  a  clean  leather  or  india-rubber  roller.  Of  course,  the 
print  must  be  re-inked  for  each  impression. 


P.  H.  Mandel's  Process  op  Making  Copies  of  Tracings. 

Abridgment  of  U.  S.  Patent  No.  294,485,  dated  March  4,  1884, 

In  carrying  out  my  improvement,  I  take  a  pane  of  glass,  which, 
preferably,  will  be  about  the  size  of  the  tracing,  or  illustration,  to  be 
copied,  and  first  cover  it  with  very  thin  collodion.  This  may  be  done 
by  pouring  the  collodion  on  the  pane  of  glass,  flowing  it  over  the  glass 
by  tilting  it  in  various  directions,  and  then  allowing  the  surplus  to 
drain  off.  When  the  pane  of  glass  becomes  dry,  I  apply,  over  the  col- 
lodion, a  material  which,  after  drying,  will  absorb  moisture  and  become 
slightly  tacky,  or  sticky,  except  where  exposed  to  the  action  of  the 
sun's  rays,  and  which,  at  such  portions  as  are  acted  upon  by  the  sun's 
rays,  will  cease  to  have  the  same  adaptability  to  absorb  moisture.  I 
have  found  that  this  material  may  be  advantageously  made  by  taking, 
say 


The  material  thus  made  may  be  applied  by  pouring  it  on,  then 
flowing  it  over  by  tilting  the  glass  in  various  directions,  to  cause  the 
material  to  flow  over  all  parts,  and,  consequently,  allowing  the  surplus  to 
drain  off.  The  pane  of  glass  thus  treated  is  then  dried,  in  any  suitable 
manner  —  as,  for  instance,  by  setting  it  over  a  box,  or  chamber,  heated 


5.   Dusting-in  Processes. 


Bichromate  of  Ammonia,      .  . 

Gum  Arabic,  

Sugar  (preferably  Grape-Sugar), 
Dissolving  in  Water,    .    .    .  . 


about  2  grams, 
about  7  grams, 
about  3  grams, 
about  150  grams. 


114 


MODERN  HELIOGRAPHIC  PROCESSES. 


internally,  in  any  suitable  manner,  or  by  placing  it  in  an  oven.  This 
should  be  done  in  a  room  similar  to  a  photographer's  dark  room. 
When  the  pane  of  glass  is  dry,  it  is  placed  in  a  frame,  with  the  tracing, 
or  other  illustration,  in  contact  with  its  side  —  which  was  treated  as  above 
described.  The  tracing,  or  illustration,  may  be  laid  in  the  frame  first, 
and  the  glass  afterward.  Care  must,  in  any  case,  be  taken  to  have  the 
tracing,  or  illustration,  smooth.  The  tracing,  or  illustration,  is  to  be 
laid,  with  the  side  on  which  the  drawing  or  picture  is  delineated,  toward 
the  treated  side  of  the  glass.  When  the  pane  of  glass  and  tracing,  or 
illustration,  have  been  fastened  in  the  frame,  the  whole  is  turned  over, 
so  that  the  back  of  the  tracing,  or  illustration,  will  be  exposed  to  the 
light.  It  is  left  exposed  for  about  20  seconds,  if  in  the  rays  of  the 
sun ;  but  if  in  the  shade,  or  if  the  weather  is  cloudy,  a  longer  exposure 
will  be  necessary.  Artificial  light — such  as  the  electric  light  or  calcium 
light  —  may  be  used  instead  of  sunlight.  Wherever  the  light  shines 
through  those  portions  of  the  tracing,  or  illustration,  which  are  between 
the  lines,  the  sensitive  material  will  be  changed,  so  that  it  will  lose  its 
tackiness,  or  stickiness ;  but,  where  the  material  is  covered  by  the  lines, 
it  remains  tacky,  or  sticky.  After  the  proper  exposure  has  been  made, 
the  pane  of  glass,  with  the  tracing,  or  illustration,  upon  it,  is  taken  to 
a  room  which  is  like  a  photographer's  dark  room.  The  tracing,  or 
illustration,  is  then  removed  from  the  pane  of  glass.  Before  removing 
the  pane  of  glass  from  the  dark  room,  I  dust  lampblack  over  its  treated 
surface,  with  a  brush,  or  otherwise. 

I  have  found  that  I  can  use  the  lampblack  better,  for  my  purpose, 
after  treating  it  with  milk.  I,  therefore,  place  a  quantity  of  lampblack 
in  milk,  mix  the  two  together  by  shaking  or  stirring,  and  then  pass 
the  mixture  through  a  fine  filter,  preferably  having,  as  a  component 
part  of  it,  a  linen  or  other  cloth.  The  lampblack,  which  is  caught  by 
the  filter,  I  allow  to  dry,  and  then  use  it.  By  its  treatment  with  milk, 
it  acquires  a  sufficient  greasiness  to  enable  me  to  apply  it  with  great 
uniformity. 

I  do  not  here  claim  the  process  described  for  treating  lampblack, 
or  coloring  matter,  and  I  may  make  such  process  the  subject  of  another 
application  for  letters  patent. 

The  lampblack  so  prepared,  or  otherwise,  adheres  to  the  tacky,  or 
sticky,  portions  of  the  sensitive  material  which  were  covered  by  the  lines 
of  the  tracing,  or  illustration,  and  does  not  adhere  to  the  other  portions 
of  the  material,  which  were  affected  by  exposure  to  the  light.  I  now 
apply,  to  the  sensitive  material,  a  thin  collodion.  This  I  may  do  by 
pouring  the  collodion  over  the  material,  tilting  the  pane  of  glass  to 
cause  the  collodion  to  flow  over  all  parts,  and  then  allowing  the  surplus 
to  drain  off.  After  the  collodion  has  dried,  I  preferably  place  the  pane 
of  glass  in  a  bath  of  water,  containing  about  1  to  1|  grains  of  nitric 
acid  to  each  gallon  of  water.    This  will  neutralize  any  bichromate  of 


DUSTING-IN  PROCESSES  SOBACCHl'S  ANTHRACOTYPY. 


115 


ammonia,  which  otherwise  might  produce  a  yellow  hue.  While  the 
treated  side  of  the  pane  of  glass  is  still  wet  from  the  bath,  I  pour  or 
run  over  it  a  solution,  consisting  of  6  grams  of  gelatine  to  every  1,200 
grams  of  water.  A  sheet  of  tracing  muslin,  or  other  material,  is  now 
applied  to  the  treated  side  of  the  pane  of  glass,  before  it  has  become 
dry,  and  is  rubbed  or  pressed  down  with  any  suitable  device,  so  as  to 
lie  close  to  the  treated  side  of  the  glass  throughout  its  extent.  It  is 
then  left  to  dry.  It  may  dry  in  the  open  air.  The  tracing  cloth,  or 
other  material,  is  finally  peeled  or  stripped  off  the  glass,  and  carries 
with  it  the  sensitive  material  which  was  applied  to  the  glass,  and  which 
had  the  original  tracing,  or  illustration,  delineated  on  it  with  the  lamp- 
black. That  side  of  the  cloth,  or  other  material,  on  which  adheres  the 
sensitive  material  bearing  the  copy  produced,  is,  generally,  to  serve  as 
the  front  or  face,  the  sensitive  material  being  transparent,  so  that  the 
lines  may  be  seen  through  it,  although  delineated  on  its  side  which  is 
next  to  the  cloth,  or  material;  hence  the  copy,  when  finished,  will  be 
a  reproduction  of  the  original,  in  contradistinction  to  a  negative. 

Anthracotypy. — This  process  was  first  described  in  a  handbook  by 
Dr.  Alexander  Sobacchi,  in  Lodi,  having  the  title  "  La  Fotantracografia 
alia  portata  di  tutti."  The  simplicity  of  the  process  attracted  the 
attention  of  Capt.  Pizzighelli,  who  thought  it  worth  while  to  study  it, 
and  give  it  a  fair  trial.  His  first  experiments  gave  very  satisfactory 
results,  and,  after  a  little  practice,  he  obtained  prints  of  such  perfec- 
tion as  can  not  be  surpassed  by  any  other  heliographic  process. 

Capt.  Pizzighelli  communicated  a  description  of  the  process,  in  a 
lecture,  in  1881,  before  the  Photographic  Society  of  Vienna,  and  also 
published  the  same  in  a  little  pamphlet.  He  says :  Sobacchi's  book 
was  published  in  1879,  and  it  is  a  pity  that  this  process  —  which  I  will 
call,  analogous  to  the  names  of  other  heliographic  processes,  Anthraco- 
typy—  is  only  so  little  known. 

Photanthracography,  in  general,  is  based  upon  the  property  of  a 
heliogram,  on  a  chromated  gelatine  film,  to  swell  up  and  become  sticky, 
in  warm  water  (even  in  cold  water),  in  those  parts  which  were  not 
affected  by  light,  whereby  these  parts  become  adapted  to  receive  and 
to  hold  dust  colors.  Those  parts  of  the  film  upon  which  the  light  did 
act,  having  obtained  a  hornish  condition,  are  indifferent  to  water,  and 
have  lost  their  adhesiveness.  # 

Requirements  of  the  Objects  to  be  Reproduced.  —  Drawings,  maps, 
engravings,  or  manuscripts,  which  are  to  be  copied  by  this  process, 
should  be  executed  on  thin  paper.  The  thinner  the  paper  of  the  original, 
the  finer  the  prints  will  turn  out.  The  paper  of  the  original  should 
show  no  dark  or  opaque  spots,  when  examined  by  transmitted  light, 
nor  should  it  have  grown  yellow  by  age. 


116 


MODERN   HEUOGRAPHIC  PROCESSES. 


From  originals  on  thick  paper,  however,  sharp  copies  may  also  be 
obtained,  but  not  by  one  operation.  In  this  case,  it  is  necessary  to 
first  make  an  inverted  print,  on  thin  paper,  by  placing  the  original  in 
the  printing  frame  so  as  to  face  the  sensitive  paper,  and  then  take,  from 
this  inverted  print,  a  copy  in  the  same  manner. 

Anthracotypy  has  the  advantage,  over  other  heliographic  methods,  of 
not  requiring  originals  of  perfectly  opaque  lines,  and  of  reproducing 
lead-pencil  just  as  well  as  black  ink  drawings.  No  one  must,  how- 
ever, expect  that  a  print  taken  from  a  pencil  drawing  will  resemble 
an  india-ink  drawing,  as  the  copy  will  look  exactly  like  the  original. 

The  use  of  drawings,  tracings,  and  photographic  negatives  and  posi- 
tives, is,  at  present,  restricted  to  such  as  are  made  in  lines,  since  the 
experiments  which  have  been  made  with  painted  drawings,  and  pictures 
in  half-tones,  have  not  been  sufficient  to  give  any  information  in  regard 
to  them. 

Coating  the  Paper  with  Gelatine. — Every  kind  of  paper  that  is 
well  sized,  and  has  a  smooth  surface,  may  be  used  in  this  process. 
For  extra  fine  work,  the  paper  should  be  selected  more  carefully,  and 
Eives's  and  Steinbach's  photographic  papers  are  preferable.  In  regard 
to  the  gelatine,  it  may  be  said,  that  any  kind  of  a  good,  white,  and 
not  too  soft  gelatine  —  which,  when  converted,  with  10  times  its  weight 
of  water,  to  a  jelly,  does  not  melt  below  86°  F.  —  is  suitable.  The  paper 
may  be  gelatinized  by  means  of  a  machine,  by  floating,  or  by  pouring 
the  "gelatine  solution  over  the  sheet.  We  confine  ourselves,  here,  to 
the  consideration  of  the  two  latter  methods  only. 

The  gelatine  solution  is  prepared,  for  both  methods,  in  the  same 
manner,  namely : 

4^  ounces  of  Gelatine  are  soaked,  for  about,  1  hour  in  |  (191) 
1  gallon  of  Water  (30  times  the  weight  of  the  Gelatine).  ) 

melted  in  a  water  bath,  and  filtered  through  linen  or  muslin.  If  the 
paper  is  to  be  floated  upon  the  gelatine,  the  latter  may  be  filtered  at 
once,  in  a  tray  of  zinc,  or  galvanized  iron,  of  suitable  size.  This  tray 
is  to  be  placed  in  a  second  and  larger  tray,  so  that  its  bottom  is  about 
1  inch  from  the  bottom  of  the  first  tray.  The  space  between  the  trays 
is  filled  with  warm  water,  which  is  kept  at  a  constant  temperature  of 
113°  to  122°  F.,  by  means  of  an  alcohol  lamp,  or  other  flame.  The 
sheets  are  handled  and  floated  in  the  manner  described  on  page  9. 
On  account  of  the  air-bubbles — which  always  will  form — the  "four  corners 
of  the  paper  should  be  carefully  lifted  up,  one  after  the  other,  so  that 
the  whole  lower  surface  may  be  examined,  and  the  existing  air-bubbles 
removed,  with  the  tip  of  the  finger,  or  with  a  small,  pointed,  wooden 
stick.  The  floating  requires  from  1  to  3  minutes,  according  to  the 
thickness  of  the  paper.    The  sheet  is,  after  this,  slowly  lifted  from  the 


CHROMIUM  PRINTS  —  SOBACCHl's  ANTHRACOTYPY.  117 

solution,  by  taking  hold  of  it  at  two  corners,  and,  when  the  surplus  of 
the  gelatine  has  dropped  off,  it  is  hung  up  to  dry.  This  will  require,  in 
a  warm  room,  from  5  to  6  hours. 

The  dry  sheets  are  pressed  between  boards,  for  about  12  hours,  in 
order  to  straighten  them.  Then  they  are  floated  upon  the  gelatine  a 
second  time,  in  the  same  manner  as  just  described,  but,  in  hanging  them 
up  to  dry,  they  should  be  suspended  by  the  edges  which  were  down 
during  the  first  drying.  This  precaution  is  necessary,  in  order  to  dis- 
tribute the  gelatine  more  uniformly  over  the  sheet. 

When  the  method  of  pouring  the  gelatine  solution  over  the  sheet 
is  to  be  used,  the  gelatine  must  be  filtered  into  a  glass,  or  bottle,  which 
is  to  be  placed  in  warm  water  (113°-122°  F.)  during  the  operation. 
The  sheets  of  paper  to  be  coated  are  immersed  in  pure  water,  one  after  the 
other,  until  they  are  thoroughly  impregnated.  Then  each  sheet  is  laid 
smoothly  upon  a  leveled  plate  of  glass,  metal,  or  wood,  covered  with  a 
sheet  of  rubber  or  wax  cloth,  and  passed  over  with  a  squeegee,  or  with 
a  leather  roller,  in  order  to  remove  as  much  of  the  water  as  possible,  to 
destroy  air-bubbles,  and  to  cause  the  sheet  to  adhere  firmly  and  smoothly 
to  the  plate.  Then  the  edges  of  the  paper  are  turned  up  about  -J-  inch, 
so  as  to  form  a  shallow  pan,  and  to  prevent  the  gelatine  from  flowing 
over  the  margin.  If  the  paper  is  thin,  the  margins  bent  up  must  be 
held  in  position  by  strips  of  wood,  placed  behind  them. 

The  warm  gelatine  solution  is  now  poured  along  the  margin,  at  one 
edge  of  the  sheet,  the  plate  tilted  or  inclined,  and  by  means  of  a 
card,  a  brush,  or  a  finger,  distributed  over  the  entire  surface.  When 
this  has  been  done,  the  plate,  or  board,  is  restored  to  its  level  position, 
and  a  second  sheet  may  be  commenced.  In  15  minutes,  the  gelatine 
will,  generally,  be  sufficiently  torpid,  so  that  the  sheet  may  be  lifted  from 
the  level  plate,  and  put  upon  a  lattice-work  to  dry.  When  the  sheets 
have  lost  a  part  of  the  moisture,  so  that  there  is  no  danger  of  tearing, 
they  may  be  hung  up  vertically,  until  perfectly  dry. 

The  last-described  method  of  gelatinizing  the  paper  has  the  great 
advantage  over  the  first  one,  that  the  thickness  of  the  film  can  be  reg- 
ulated with  certainty,  by  simply  measuring  the  quantity  of  gelatine 
which  each  sheet  is  to  receive ;  while  in  the  method  of  floating,  the 
thickness  of  the  coating,  and  uniformity  of  the  same,  depends,  to  a  great 
extent,  upon  the  temperature  of  the  atmosphere. 

The  gelatine  solution  required  is, 


For   1  square  inch  of  paper  surface,   0.01351  fluid  ounce. 

"    74  square  inches       "  "    1  fluid  ounce. 

"     1  square  foot  "  "    2  fluid  ounces. 

"     8  square  feet  u  "    1  pint. 

"    64  square  feet  "  "    1  gallon. 


The  liquid  solution  will,  accordingly,  cover  the  paper  about  ^\  of  an  inch. 


118 


MODERN  HELIOGRAPHIC  PROCESSES. 


J.  Husnik  recommends  to  pour  the  gelatine  solution  through  a  small 
hair-sieve,  which  is  held  very  close  to  the  paper,  as  hereby  the  forma- 
tion of  air-bubbles  may  be  entirely  avoided. 

If  protected  from  moisture,  the  gelatinized  paper  may  be  preserved 
for  any  length  of  time. 

Sensitizing  the  Paper.  —  The  paper  is  sensitized  by  immersing  it 
for  1  or  2  minutes,  in  a  solution  of 


If  it  is  desirable  to  dry  the  paper  as  quickly  as  possible,  the  sensi- 
tizing solution  may  be  composed  of 


The  addition  of  alcohol  also  diminishes  the  formation  of  air-bubbles. 

An  addition  of  ammonia  water  to  the  sensitizing  solution  is,  also, 
an  advantage,  as  the  double  salt  of  bichromate  of  potassium  and  am- 
monium, which  is  then  formed,  is  more  sensitive  to  light,  and  more 
durable,  than  the  bichromate  of  potassium.  In  preparing  the  sensitizing 
solution  with  ammonia  water,  1  ounce  of  potassium  bichromate  may 
be  dissolved  in  10  or  12  fluid  ounces  of  pure  water,  and  so  much 
ammonia  water  added  until  the  reddish  color  of  the  solution  becomes 
yellow;  pure  water  is  added  to  make  the  whole  amount  17  fluid  ounces, 
and,  finally,  the  8  ounces  of  alcohol  are  added. 

The  alcohol  and  ammonia  water  are,  however,  not  absolutely  neces- 
sary for  obtaining  perfect  prints. 

The  sensitizing  solution  must  be  used  as  cold  as  possible.  In  sum- 
mer, it  may  be  kept  in  an  ice-chest,  for  a  few  hours,  before  using  it. 
The  reason  for  using  the  sensitizing  solution  cold  is,  that  the  solution 
will  dissolve  a  small  amount  of  the  gelatine,  and  the  colder  the  solution 
is,  the  smaller  this  amount  will  be.  The  alcohol  assists,  also,  in 
preventing  the  gelatine  from  being  dissolved. 

During  the  sensitizing,  the  sheets  should  be  turned  over  a  few  times, 
in  the  bath,  and  adhering  air-bubbles  removed  by  means  of  a  little 
hair  brush. 

The  sensitizing  tray  may  be  made  of  zinc  or  galvanized  iron.  After 
sensitizing,  the  sheet  is  hung  up  to  dry,  except  when  it  is  intended  for 
very  fine  work.  In  this  case,  it  is  to  be  squeegeed  down  upon  a  clean 
plate  of  polished  glass,  which  was  previously  thinly  coated  with  talc, 
wax,  or  an  alcoholic  solution  of  ox-gall  (1  to  10),  the  latter  allowed  to  dry 
on  the  same.    Before  using,  the  edges  of  the  sheet  should  be  trimmed,  and 


Bichromate  of  Potassium, 
Water,  


1  part. 
25  parts. 


.  (192). 


Bichromate  of  Potassium, 

Water,  

Alcohol  (proof),   .    .  . 


1  part.  \ 

17  parts.  [  .  (193). 


8  parts.  ) 


CHROMIUM  PRINTS  SOBACCHl's  ANTHRACOTYPY. 


119 


then  the  sheet  taken  from  the  plate.  It  requires  from  5  to  8  hours  for 
the  paper  to  dry  on  the  glass  plate — while  a  free  hanging  sheet  will 
become  dry  in  from  3  to  4  hours  —  but  the  paper  receives  a  perfectly 
smooth  surface,  which  insures  a  close  contact  between  the  sensitive  film 
and  the  original  drawing. 

The  sensitizing  may  be  done  by  weak  daylight,  as  the  chromated 
gelatine,  in  a  wet  condition,  is  but  very  slightly  sensitive  to  light. 
The  drying,  however,  must  take  place  in  a  dark  room,  because,  in  a 
dry  state,  this  paper  is  more  sensitive  than  chloride  of  silver  paper. 

The  sensitized  sheets  may  be  preserved,  for  about  a  week,  if  a  few 
pieces  of  sesquicarbonate  of  ammonium  are  placed  in  the  same  box,  or 
drawer,  in  which  the  paper  is  kept,  so  that  the  latter  will  be  in  an 
atmosphere  of  ammonia  vapors.  In  all  cases  it  should  be  used  as  soon 
as  possible.  Prints  made  on  freshly  prepared  paper  will  always  give 
better  satisfaction  than  when  made  on  old  paper. 

The  Exposure  to  Light  requires,  for  originals  made  on  tracing  paper, 
or  tracing  cloth,  from  20  to  25  minutes,  in  the  sun.  When  the  image 
is  faintly  visible,  in  light-yellow  lines  upon  a  brownish  surface,  the 
exposure  must  be  discontinued.  Over-exposure  is  less  detrimental  than 
under-exposure,  because,  in  the  first  case,  the  print  may  be  saved  by 
using  warmer  water  in  the  next  operation  of  developing ;  in  the  second 
case,  the  print  will  be  lost. 

The  Development  op  the  Picture.  —  The  copies,  when  taken  from 
the  printing  frame,  are  plunged  into  cold  water,  which  must  be  renewed 
as  often  as  it  receives  a  yellow  coloration  from  the  dissolving 
chromic  salt.  Then  the  prints  may  be  developed  at  once,  before  drying, 
or  they  may  be  hung  up  to  dry,  and  preserved,  in  this  condition,  for 
any  length  of  time.  In  the  latter  case,  they  must  first  be  soaked  in 
cold  water,  when  they  are  to  be  developed.  In  order  to  develop  the 
image,  the  print  is  taken  out  of  the  cold  water  bath,  the  water  allowed 
to  drop  off  it,  and  is  then  immersed  for  1  or  2  minutes  (not  longer),  in 
lukewarm  water,  of  82°  to  86°  F.  The  lines  of  the  print,  which  were 
protected  from  the  action  of  light  by  the  black  lines  of  the  original, 
will  now  swell  up,  appear  in  relief,  and  become  somewhat  soft  and 
adhesive.  The  print  is  then  placed  upon  an  even  support  of  glass, 
metal,  or  wood,  and,  by  means  of  blotting  paper,  or  by  touching  it  with 
a  tuft  of  soft  cotton,  or  by  passing  over  it  with  a  clean  leather  roller, 
is  superficially  dried. 

Then  the  color,  in  the  form  of  an  impalpable  flour,  is  sifted  over 
the  whole  sheet,  and,  by  means  of  a  soft  marten's-hair  brush,  is  rubbed, 
in  circular  movements,  over  the  lines  of  the  print.  The  color  will 
adhere  to  the  soft  and  sticky  lines,  and  so  a  positive  picture  will  appear. 
Ordinarily  the  ground  will,  also,  become  more  or  less  tinted ;  but,  if  this 


120 


MODERN  HELIOGRAPHIC  PROCESSES. 


is  not  caused  by  under-exposure,  it  will  have  no  influence  upon  the 
final  success. 

After  the  dusting-in  process  is  finished,  the  print  is  dried  in  a  warm 
place :  in  summer,  in  the  sun ;  in  winter,  near  a  stove,  or  in  a  drying- 
box.  This  is  done  for  the  purpose  of  softening  the  gelatine  still  more, 
so  that  the  loosely  adhering  particles  of  the  coloring  material — in  conse- 
quence of  the  superficial  melting,  and  the  later  drying-in  of  the  gelatine — 
will  be  embodied  with  the  gelatine.  The  drying  temperature  ought  not 
to  exceed  140°  F.,  or  the  gelatine  will  flow  on  the  sheet.  When  the 
print  is  perfectly  dry,  it  is  plunged  into  cold  water  again,  laid  flat  upon 
a  plain  support,  and  the  superfluous  color  removed  by  means  of  a  soft, 
wet  sponge.  If,  after  this  operation,  the  lines  appear  clean,  and  uni- 
formly colored,  upon  a  white  surface,  the  print  is  hung  up  to  dry,  and 
may  be  considered  finished.  If,  however,  the  color  adhered  only  in 
some  parts,  and  not  in  others,  or  when  the  coloration  appears  to  be  too 
pale,  or  unequally  distributed,  the  dusting-in  process  may  be  repeated, 
as  often  as  necessary,  to  obtain  a  satisfactory  result. 

All  colors  which  have  no  tanning  effect  upon  the  gelatine,  may  be 
applied  in  this  process.  For  reproducing  black  line-drawings,  lampblack 
or  finely  pulverized  charcoal  are  the  most  suitable.  Other  colors,  such 
as  plumbago,  ultramarine-blue,  ultramarine-green,  sepia,  vermilion,  and 
gold  and  silver  bronze  may  also  be  used  with  success. 

Causes  of  Failure  may  be 

1.  Unsuitable  color. 

2.  Over-exposure. 

3.  Old  sensitized  paper. 

4.  Unequally  gelatinized  paper. 

For  the  first  and  fourth  faults,  several  repetitions  of  the  dusting-in 
process,  for  the  second  and  third,  an  increasing  of  the  temperature  of 
the  water  bath  to  104°,  122°,  even  to  140°  F.,  will  be  found  of  advantage. 

Paper,  gelatinized  as  described  in  this  process,  can  also  be  used  in 
Papyrography  (page  112),  and  for  copies  in  printing  ink  (page  78). 


XII. 


PROCESSES  WITH  SALTS  OF  URANIUM. 


The  nitrate  of  the  sesquioxide  of  uranium  (U02y2N03-\-6H20)y  in  the 
presence  of  organic  substances,  is  reduced  by  light,  as  in  the  case  of 
the  sesquichloride  of  iron.  This  discovery  was  first  made  by  M.  Niepce 
de  St.  Victor,  and  by  Burnett. 

The  paper,  without  having  undergone  any  preceding  preparation  — 
excepting  that  of  having  been  excluded  from  the  light  for  several  days — 
is  sensitized  with  a  solution  of 

Nitrate  of  Uranium,     ....    1  part.  )  (ioa) 
Water,  16  parts.  )  '  * 

The  strength  of  the  sensitizing  solution  varies,  according  to  different 
authorities,  from  1  to  5,  to  1  to  33^,  to  1  to  96.  We  have  used  a  solution 
according  to  formula  (194). 

The  paper  may  be  floated  upon  the  solution,  or  it  may  be  coated 
therewith  by  means  of  a  brush.  It  must  be  hung  up  to  dry,  in  a  dark 
place.  The  sensitized  paper  can  be  preserved,  in  the  dark,  for  a  consid- 
erable time.    1  ounce  of  the  solution  will  cover  9  square  feet  of  paper. 

The  exposure,  beneath  a  tracing,  requires,  in  the  direct  rays  of  the 
sun,  from  10  to  15  minutes ;  in  diffused  light,  from  1  to  2  hours. 

The  image  thus  produced  is  very  faint  and  indistinct,  but  it  may 
be  brought  out,  in  various  colors,  by  one  of  the  following  developers : 


Developer  for  Black  Pictures. 

Silver,  1  part. 

Distilled  Water,  30  parts. 


Nitrate  of  Silver,  1  part,   j  (195) 

s.  ) 


The  print  may  be  immersed  in  the  solution,  or  the  latter  may  be 
applied  with  a  brush.  The  image  comes  out  very  rapidly ;  in  30  to  40 
seconds  the  development  is  complete.  The  prints  are  fixed  by  simply 
washing  them  thoroughly  in  water.  Some  authorities  recommend  to 
immerse  the  prints,  before  developing,  in  warm  water,  of  120°  to  140°  F., 
in  order  to  remove  all  the  soluble,  unaltered  uranic  salt.  Others  use, 
for  the  same  purpose,  cold  water,  acidified  with  a  few  drops  of  hydro- 
chloric acid.  (The  nitrate  of  silver  developer  is  given,  by  some  author- 
ities, as  1  to  17.) 

121 


122 


MODERN  HELIOGRAPHIC  PROCESSES. 


Developer  for  Red-Brown  Prints. 

Ferricyanide  of  Potassium,  .    .    1  part.   )  /-|q/>\ 
Water,  48  parts.  )  '  * 

Proceed  as  with  the  nitrate  of  silver  developer.  The  image  will  appear 
in  a  few  minutes,  and  is  then  to  be  rinsed  in  water. 

The  red-brown  picture  thus  obtained  may  be  converted  into  a  dark 
greenish-gray  one,  by  immersing  it,  before  dry,  in  a  solution  of 

Sesquichloride  of  Iron,    ...    1  part.  )  (iqj) 
Distilled  Water,   48  parts.  )  * 

and  washing  it  again. 

Fine  green-colored  prints  are  made  (according  to  Dingler's  Pol. 
Jour.,  v.  152,  No.  6),  by  immersing  the  red-brown  picture  in  a  solution 
of  cobaltous  nitrate,  for  1  minute,  and  fixing  it  in  a  solution  of 

Sulphate  of  Iron,  1  part.  \ 

Sulphuric  Acid,  1  part.  >  .  (198). 

Water,  25  parts.  ) 


Developer  for  Violet  Pictures. 

:  Gold,  1  part. 

Water,   240  parts. 


Chloride  of  Gold,  1  part,  j  (199) 


The  uranium  print  is  immersed  in  this  solution,  and  then  thoroughly 
washed. 


XIII. 


TWO  METHODS  FOR  PRODUCING  THE  ORIGINAL  TRACING 

AS  A  NEGATIVE. 

The  following  are  two  methods  by  which  tracings,  in  white  lines 
upon  a  dark  surface,  may  be  produced,  so  that  the  prints  obtained  from 
them,  by  an  indirect  process,  will  be  positives,  in  dark  lines  upon  a 
white  ground.  The  first  of  these  methods  is  according  to  Haugk  and 
Liesegang,  and  the  second  was  first  published  in  the  "American 
Machinist." 

First  Method.  —  The  tracing  is  made  on  paper  with  black  lithographic 
or  autographic  ink.  Great  care  must  be  taken  that  the  drawing-pen 
does  not  cut  into  the  paper. 

When  the  tracing  is  dry,  it  is  stretched  upon  a  drawing  board  in 
the  usual  manner.  Under  the  tracing,  a  sheet  of  blotting  paper  is  to 
be  placed.  The  entire  drawing  is  then  coated,  once  or  oftener,  with  a 
concentrated  solution  of  aniline-brown,  by  means  of  a  wide,  soft,  flat 
brush.  After  drying,  the  drawing  is  treated  with  a  tuft  of  cotton,  or  a 
sponge,  dipped  in  oil  of  turpentine,  until  all  the  lines  appear,  in  a  clear 
white  upon  a  dark  ground. 

Second  Method.  —  The  drawing  is  traced,  on  paper,  with  a  solution 
of  citrate  of  iron  and  ammonia.  When  dry,  the  surface  of  the  sheet  is 
blackened  by  means  of  a  crayon,  soft  pencil,  or  plumbago  powder. 
Faber,  the  lead-pencil  manufacturer,  offers  for  sale  pulverized  graphite, 
which  is  very  suitable  for  this  purpose.  The  sheet  is  then  immersed 
in  water,  in  order  to  dissolve  the  ferric  salt,  and,  finally,  it  is  dried. 


123 


XIV. 


TABLE  OF  CHEMICALS 

Mentioned  in  this  Book,  their  French  and  German  Names, 
Molecular  Weights,  Molecular  Formula,  Composition, 
Average  Price, 
Remarks  Relating  to  their  Principal  Properties 
and  their  preparation. 


i>9£ 

lis  a 

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B  So°rd 

0  _3  & 

GO  0«w  OQ 

«£§| 

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a :.d  d 
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03  Q  d 

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cj£d 
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a>  n  © 

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£  d  ftr3  ^55^0^0 

Ord^-g  d  0^-° 

P,P,Or=l  <S  ©rd  ej-grOrOd 


-d  ~,2  o  00  „ 
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3  LT«w  ^  03  bo  2 
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d  8B.Q  SS-5  ft 


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I  bo 


Acetic  Acid 
mixes  with 


water  in  all 
proportions. 


In   all  proportions. 


In   all  proportions. 


Average 
Price. 


Melting 
Point,  F. 


Boiling 
Point,  F. 


Specific 
Weight. 


S  a  w 

W  „ 

88  So 

»o  ^ 

«o  K 

o 


O 
°.  o 


ed  O 
-  WO 
w  o  W 

00 

O  " 
co   


o 

O  tti 
r~  to 
o  °°. 


^  O 

CO  M 


Molecular 
Weight. 


<M  O 
Ol  rH 
iH  CM 


O 

y  o 


1 

§  I 

OJ  >> 

u  -d 

o3  d 

o  <! 

d  . 


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■d  to  : 

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o  S  cq 

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iii 

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O    O  OJ 

000 

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CD 

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6  j.  Q 

d  ^  d 

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W  S   :  + 


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2  s,2  ^"K  £e  c  2  S   .2-  04 


3  £+3  d  u  S  ftc3,Q 


£  Or= 


Parts  of 
Water 
required 
to  dissolve 
1  part. 

b£ 

0 
fi 

rH 

in  all 

cold 

propor- 
tions. 00 

CM 

^      In  all  proportions. 

Average 
Price  

per  glass 
bulb, 
$1.00 

per  rb 
30 

1.00 
1.50 
50 

per  oz. 
40 

25 

25 

per  lb 

65 

per  gal. 
2.40 

8 

to' 

Melting 
Point,  F. 

0  00 

rH          lC  CO 
CO          i-H  O 

1  " 

CM  tO 
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CO 

0 

lO 

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Boiling 
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O  O 

S  8 

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& 

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I- 

Specific 
Weight.. 

1.97 
1.8426 

1.124 

1.74 

0.817 
at  60°F. 

0.838 

0.7939 
at  60°F. 

o  ^ 

co  « 


o      o  u 


Molecular 
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2  g  cJ 

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Boiling 
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Specific 
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Molecular 
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g"d.o3ccr^ 

M  50  rj  -hTh  Ph  « 

ftog^^-g* 

.2  S  a'g  03  o^s 

03  d  03  O  >» 
So^  03  d  ^XiPf 

,d.2  «  ft  . 
fco  M.Ba'S'S  §2 

m  00  CPhj««  ?  so  H  SO 


Parts  of 
Water 
required 
to  dissolve 
1  part. 

boil'gl 

cold 

7000 

Average 
Price  

per  15  gr. 
$0.75 

per  oz. 
38 

per  rb 
1.00 

85 

Melting 
Point,  F. 

0 

OJ 

1 

Boiling 
Point,  F. 

>  0 

O  tN 

«« 

Specific 
Weight.. 

1.31-1.48 
4.9481 

CI 

co' 

100  parts  of  the  Com- 
pound contain. 

64.86  Au;  35.14  CI 

O 

w 

w 

0  § 
s  § 

0  co 

5S  " 

~  CU 

O 

w 

CN 

ir| 

<M 

O 

H 

o> 

rH 

00 

Molecular 
Weight.. 

303.5 

CM  CN 

rH                         CO  lO 

o  -g 


iff 

o 
O 


a 

d 

O 


3| 

o4  d 
I? 

03 

a  3 
a  2 

O  ^ 


li 


2  ^ 
'd  o 

7  I 


S    r^  » 

-d 
o 


-d 

o  . 

"Eh  'Eh 

o  o 

rd  rd 

CJ1  ra 

CO  *rH 

CD  ft) 

Ti 


« I  a  ri 

5 '15  ^  g 

a « a  § 
.2  •  .2  § 

d 'd  d  a> 
2  a  2  fl 

a  •§  a  2 
ilia 

1  £ 


5       ■  rd 

>,  ®  -d 

« a  & 

rH  O 

<u  >>  d 

S  rd  «> 

03  co 


-d  cp 
t>»  Ph 
W  I 


[1301 


•2d** 

d-d  £a 


be© 

d  M 
|  o 
ft 

-© 

2d 

CJ  O 

aJ 


£'3.25  °© 
•o  o  ^  o  cp",32 
'S  2  ©  »  S  ©  I 


5*^ 


fl  o 
ft 

03 

*  © 


_,  O  co  © 

o  o 


X 


©  a)  d-~  ^-rtw 


V£  .  d 


3-ai.2 
SI** 

£  >..25 

©*  ©  03 

fa 


c-d 

x  2 
d  > 


1  o- 

'  U  0)  03  Or] 


cc  "S-d 
©,2  to 


-2^ 

0  O 

"2d 

©  o  o3 m  «  fe 
■g  =3    d  ©  2  • 

a.^ej.d-S  ^ 

1  s  s  g>i|U 

OoOfHfld^' 

SSftSSC'g.S 

•2<E>f  ^g-M 

fa 


"S'£  S  S  £  ri 
g^p&ftS 

~h     bc-~  co 

>   O     >     >  fH 
£  © 

O  •>  co  ^cSrt 
co  03 bCditZ 

©  >\d  ^  2  22  «3 

Cd5  s  *g . 

c3  ©        S  rd 

*  G    ©  co  a>  t3 
0  ©2  o 
•SS  2  ftw  03 ^ 
0  ©  03  S  o-s 
■g-e  2  o-Q+J.2< 

g.g  g  ©  c3-d  O 
■p-d  o3  cp      ^  cp 


ftoVv  m  d 


2  a 

2 

d  d 

•rH  O 

DD  d 


Is 


Parts  of 
Water 
required 
to  dissolve 
1  part. 

boil'g 

eo 
0 

cold 

Average 
Price  

per  Tb 
$0.60 
06 

35 

per  oz. 
10 

per  lb 

62 

per  oz. 

25 

Melting 
Point,  F. 

Pure 
Com. 

Boiling 
Point,  F. 

Specific 
Weight.. 

t» 
°i 

100  parts  of  the  Com- 
pound contain. 

ra 
O 
CO 

10 

Si 

O00. 

CN30 
©  <M 
fa 

9 
00 

CM 

Molecular 
Weight.. 

<N 

to 

tO 

©  '03 

■O  H 

s  £  "C 

*    M  S 

c3  iJ  fa 

x  9  1 

o  I  i 

°  r*"  ^ 

•c  fe.  O 


3* 


d  +3 

0  o3 

1  ° 

"0  *c 


p3  ^  fa 
M    ©  c! 

^  ©  d 

§  *  "2 

d  0  o 

8  3  a 

IP] 

S  I*"  JS 

fa 


2 


©  4J 
ft  tj 

+^  o 

©  x} 

.©  B 


s3 
H 

O  ©  fa 
H3  1 

0  ©  3 

'  -a 

M 
I 


H 


•H    g  CO 


s  S 

o 


03  c3 


^  c  ^d 


^3  a 
^  !=■  fa  CO 

co  I  '. 


d 

SI 

CO 

CD 

CO 

03  Ph 

fa 

0  V 


45  =3 

tp  +3 

©  a 

o3  u 

t~  z> 

t,  03  fa 

«  ^  I 

■c  » 


11 

.2  © 
I  a 

It 


%  d 
o  'C  '53 

s.^f  I 


[131] 


Parts  of 
Water 
required 
to  dissolve 
1  part. 

boil'g  | 

9000 
0.15 

0.15 
3 

|  cold 

o?                        "»             <o                   <o  o 

SSS2$j2f  go 

.d  cj  =3  ~.  2  OVd_  » 
d  2  f* 

2>,d  J 


be 


o 


go  .* 

O  l  ai-p_i 

od 


>,csd 

'i 

ex.: 


•S  03  r*d 


£  ©  „  S  OB*?©  CO 

a'Ch  S  g-g  fv5 

fc'gftooB^SS.S 
.SEgaSgSsSS 
.a  2  o  5  os  S*»  2^  a 


o  aj,a£, 

gjfl  0>  «  >  P  <D»d  C- 

da§8S.2>^g 
.2  2'£.2^>  d"S  ^ 

gain  j  e"°~ 

.2.2  8.25 

"w  3  d  t3  _: 
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a-' 


o  o  ©  o 


o  d 


h  So  §  ft^  2*  d 


IflllljUi 

g£  w«PH'd  oPnd  ra 


■2  ©d  oh 
ft  d 

J3-C.2  *  2 
!2ft3S3 

M 


0  o 
boo 

£,a  6Xd-"S 

O  03  w  a> 
ft^gH 

rgd^.2 


lull's 

<^d  .05 

2  <-<-^ 
»h  to  d  .r-S 


Average 
Price  . 


£  8 

M  o 

2 
P* 


Melting 
Point. 


Boiling 
Point. 


Specific 
Weight. 


O 

M 

CJD^ 


O 

cc 

CM 
CO 

O 

tJO 

a. 


Molecular 
Weight. 


W 

10 

a 

o 
W 

1i 

O  d  4 

O  60  pj 
60  03  d 

^  5 .2 

fl  eS  « 

o  d  2 

r>  o  H 
03  * 

O  «  2 


.2  6 

BO  +5 

o  os 

P  is 
i3-d 

a  a 


2^ 


4>  vj  s 


^  2 

w    I    ,  • 

^  5."  I> 
03 

2 


2  ^ 

d  60  d 

— '    03  0Q 

sag 

1  0  .2 

■3-2  S 

.  —3  03 

a  1 2 

w    I  .• 

2  ^  ^ 
2 


„  3 
'Sou 
d  S  ^. 

^  0  ^ 
®  0  *d 

>  o  "oa 
K  d  ^ 

o  s  o 

ill 


^  o 

d  m 

§  a 

^2  d 


a  w  1 


BOS 

a  5  0 

OSS 

5  a  ft 

2  2ft 
If?. 


S3 

a  a 

a>  o 
d  " 
111 

o  -a  .2 
w  1  "3 
a  w  1 

•2  I.  i 


[132] 


•Ed  >.o 

"~  2  E  »  , 

g  o  a***,' 
dS^-S 
«>2S 

o  o  2d 


5*1  < 

Cd  U 

nil 

©  a>  03 

S  « 

£  OS  03 


3"C  o 

<=\2S 

Sod 

S3 


a>  d  o 


•dta      o  «  2  >, 


0  bC'3  °C  v 

o  ^  bt!  g««  w> 
a>~x|a.d,dod 

P  03  p<M  ^5  S-°i2 


8  23  s  a 


c3ftOc3a>£<,r,-^w 

g  8.2-9  f  &£ga> 
E  <u  fl  c  bca>  £  £,d 
©d  aj  §  dd  03 


W  r— I  d  d 


,d  -r—  ca  u 


ft;>d 
O  a>'d 


IQ  4)  Cj  OJ    •  • 


0) 


c3  £>- 


3  — ^.d  S  oi 
pd  03  M 

+»  JSi-H  O  03«*H 

wd.g'S 
S  o  2  ^  ».d 

°§-2s5dS 

O  <a  ^0.2^  > 

2  3  d  oj  3 


«♦-.   d  >  . 


Average 
Price. 


2s 

ft 


Melting 
Point,  F. 


Boiling 
Point,  F. 


Specific 
Weight. 


MO 


o 

oO 


Mo 
"  Oi 
to  • 


Molecular 
Weight. 


~  3 


§•§  i 

©   03  d 

2  1  i 


3  ^ 


P 
IT 


+j 'd 
-d  -g 

a 

E3 


2  a>  a 

a  5^ 


Ti 


2  3 


O     .  03 

o3  OJD 

o  ^  d 

Sis 

d  . «  o 
£  w  « 


1  ^ 


o 

"  % 

a.  o 
+  p. 

.  a> 
^  A  -a 

o  «    .  +3 

—  a    fli  ni 

1^ 

o  a) 
ft  d 

,2  « 
d  3 

d 
3 


fa  ^ 


M 
s  * 

a^ 

d 


d  CQ 
S  d 

>>  o» 

2  ^ 
i-»  d  d 

<B   CU  03 

ill 


ft  - 


o  W 


I.  O 


•  -  03 

•d  d 

d  I 
w  I 
aS 

5 


+2  *? 


[133] 


_0j  O  rH  a      £  -\-^B 

O  d  bOjd-rHr^WH  p1-1 

d  0o^£  d 

«3  ^  o3  o3  M  o3^  ft  d* 
[d^  oi  o--r;  K.3fl3 


e  £  he'd  i«'HJ,.;d 


P.d'dT!  d  0  -coo 


^  d  "  f      H  Oft 

<  r!  :  ai  n  n  O 


d  p«S 


„"0&   d  _ 

PiS  bcS^ 

"-CC  X  03  to  rj  ^ 

o  2  bor-  ■ 


"Sold  «  d  ^  >_d"-3 
03  P  d  © _Q)-r<  03 

•  s  03  >  05 
d  -h  p  o>  d  03 

SOlOOjOOfflr'HO 


d  0> «  o3  3 

3  5  •  &s  ^ 

"^•2£  dp7>. 
rO.  03  .2.5 

o  S3  " 


^2 


ft  o  co  >rt 

gS^cl^o 

K,  o  .73  -2  bo  w 


6|iSSd.2 

d  S^t?  d  o  o> 

2,2 

°3 *j  »h  f-1  j, 'd X! 
rd'-j  d  Ol  T  03  " 

d2dtj^0 

•h  03  w+a  aJ'g  h 

o>  o  ®  a  2-d 
S  ®c3'S  d«o 

a?,S^ds^ 

n 


as 

o  to 

O— ( 

SI 

AMI 
bo  0>^3 

•H  CO 

>,d'P. 

B^S 

ft  -co 

d  o  o 

•os  a 

III 

Pi 

U3 


Parts  of 
Water 
required 
to  dissolve 
1  part. 

boil-gj 

cold 

CO 

Average 
Price  — 

per  oz. 
$0.20 

per  lb 

35 

50 
1.75 

per  oz. 
2.25 

Melting 
Point,  F. 

h                ?h  : 
S                 Si  : 

Boiling 
Point,  F. 

Specific 
Weight.. 

O 

ci 

6.353 

100  parts  of  the  Com- 
pound contain. 

m 
O 

CM 

0 
W 

a 

^                 88  « 

O                         -5  bo 
d                          «  < 

3           0  ^ 
5           s  « 

CN  I- 
O  10 

Molecular 
Weight. . 

GO 

SSI 

a 

d 

"to 

CO 

0  t-c 
ft  .TS 

01  d 

S  S  3 
a*;* 


d  5 

^  03 

! 

to  d 
to  d 


to   ^  S 

1 


I  g 


a>  d 

H  CO 

1 


d 

SP 

s  a^ 
w  1  i 

> 


[134] 


0)rr)  0>+->-d  *-> 

0)  fi  OS  0 


51  2 ,2  00  ^^r-^o 


as  sag 

ca      t-i  f-i  W 

3*3  Sjs  s 


"  o>  d,~  os  « 

p.  o> 


"S  —  c  £  <u  q>  s>  o 
?  <*-  ,d  °J  d *^ "S ts 
®oot'o,?Cd 

O  co  o> 


t5  ° 
d  *« 
o,d 

FL  03 

Ci>rH 


a  o  g  >.*-  S  H 


S3  w 

ost3  M 

ted  d  3 
d-^  o3  > 


£  o3  OJ'O  'g^^a 

tTd  ^d  03  H 
a)  cy-H  o  2  &    r-c  ^  ^ 

oSgsSg^ld'S^SS 

2o3^d.dcN1-ioSa<^^c3P, 

o 


£03 

Q  Q    -.    03   .,   m  CJ  ** 


P.oji-t  d  o 

a>  "o  d-2 

•2^°-2s 
£d.23d 

r-H  x  co  d  03 

33 


d  o«~*^  °  <» 
o3^-rtl_,+53 

p.S'bc?,  s-8 


0) 


00  d  ^2^ 
O  O  0)  ™  bt'+-i 


053 

OS  «  o£ 

os  c3  o  ,*>  —.S 
55  .  P"  os  W 

-«fl-dS^o.2«o 

-         O  2  03 

G9  o 


11*1 

*^  o  °  o3 
^£-~.3d 

d  d  ^  - 
g«.2  3' 

d  03  J3 

^  d 


>>o3 

2  a 

oj  d 


o  _ 


,  03  O  X 

3-dft^| 
So  « 2^^ 

H  o>  >-  R-r3 
,03^^  ^d"g 
■O  03>^  c3  03 

d      °>?S»  o 

a>    o>  +^  p.-g  -d  a 

n  03 "^•d-'^ 

3  d-2^*io^ 

fl-S 

IS  055? 
pq 


Parts  of 
Water 
required 
to  dissolve 
1  part. 

be 

o 
& 

cold  | 

Average 
Price  

per  oz. 
$1.50 

1.75 
90 

per  lb 

50 

12 

Melting 
Point,  F. 

Boiling 
Point,  F. 

Specific 
Weight.. 

5.55 

5.602 
4.355 

100  parts  of  the  Com- 
pound contain. 

,_,                                                    n                        O  ft 

CO                                       M                        j"                               W  O  « 

ri»                   «                         t-JT"  coO 
cn                                  .  -                    co                           eoj?  Std 

bu                                „W  .-7: 
^                      <              o                  c£  OJ2 

N                                                              <Jj  » 
jo                                                        oo  ccM 

*°                           cm"  <° 

Molecular 
Weight . . 

143.5 

235 
170 

136 

84 

^  0> 

o  -d 
3  "g 


d 

5-2  §> 

^.2  1 
'd  as  d 


be  ^ 
I 


d  o 
bo  nd 


•d  -d  S 

'd  i— i 

o  I  I 

H  U 


d 

be  +j 


-d  -a 

If 


o 
w 

co 
+ 
O 

0) 

w 

o 

o3  . 

H»f  o3 


II? 


X  O  03 


«  pq 

a. i 
a  $ 

•d 
o 

02 


[135] 


03  L  $ 
2  ft^ 


-3  a) 


,^2  <»  5  g  o> 

o^gss  H,a 

« 3  life 

^  0>  3  0>  ^ 

o  o 


r^,-  3        3  P  03  »  M 

re  3 ^     2  w  b  S*S 


'S'SS.SrebS 

o 


5  3.3 

H 


■d  o>  P 


o  ^  E  re  3    -g  w 
g"3     re  £gd 
P>2g^3£re.£ 
P^O  P-M  ©  P.5  £ 

jd.S  o,P  «S  ►  P<P 


111 

03,3  w 
re  ui 

fO^l  53 

o  f5  a* 
-0  2  8 

o3  o  o 
3-r|  bfiN 

•St;  ^  re 

*d  °  o  >. 

tt-..i5  >  o 
h  ^  ©  w 


rrt  re 

O  4> 

o  2 


11 

•a* 


^  d.-S'd 

°  re      «  £ 

23 n  a  o-s 

re'd  © 

o3  o3  g  re  3 
©   »  d     i— i 

a  w-d  o 
•w.b'd  3  2 
p|  S  3 

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r3  re  c3  c3 


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puu 

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—  3 


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a>  pj 
PI 

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CO 


r-i-d^rd 

03  >  2  2  >» 

r-H  O  O  0)  °* 


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d  +2  *i      w  "li  •  Pi 


o  o 

S'S36 

•"A  p/2 

si 

p  £  d 
«  >  o& 

O  SB'S  3 

re  ^-S-d^ 

|g.2 

2S  O 

03  Q>+3 

w 


d 

lrd  03  323 
,  3  «X3 
i  03-^  k« 


^  a3 

m  o 

jd 

3 


O 
dg 


re  pt, 
II 


a  a  ^  § 

03  bc2,2  « 
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^  S  0rd 
■S  S  o  p  § 

p  a>  o3  i— < 
g  >,Q7d  « 
.2  o  ^  a>  o 

CO 


Parts  of 
Water 
required 
to  dissolve 
1  part. 

boil'gl 

cold 

ei  ei 

Average 
Price  

per  R> 
$0.10 
1.00 

25 

1.00 

55 

Melting 
Point. . . . 

Boiling 
Point... 

anhyd. 
cryst. 

Specific 
Weight  . 

2.509.. 
1.454.. 

2.16 

in  ; 

CI 

ei 

100  parts  of  the  Com- 
pound contain. 

CI 

8  s 
^  s 

O  03 

O 

H 

si 

o 

03N 

5zi 

o 

°«  5 

"eo  o3 

Molecular 
Weight.. 

106 
58.5 

o  ; 

1  a 

a 

o  d 

re  O 


5  5  § 

«  03  s 

O  S  H 

■S  •£  t5 

o3  o3  ^ 

a  i 

.a  £  s 

-d 
o 

CO 


CO 


a  . 

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%  M 

CO  § 

Is-- 

o  °  -2 
o  w 

o  o 

o-0  a 

2  2  .2 
S  g  £ 

a  • 

3  S 
.2  t*,  <i5 

•o 

O 

CO 


9  I 


O 

a 

.2&;<5 

•d 

o 

CO 


o3  g 

•d  *d 

w  w 
a  i 

•d 

o 

CO 


-d  w 

O 

'd  >• 

>>  M 

xi  o 

a  a 

3  3 


03  b 


I 


a  *- 

o 

CO 


'd  re 

+3  P< 

3 


p)  P 


re 


d  d 

3  I 


I 


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P 


^  d  .2  ~ 

°  J3  'd  ? 
3  o>  o  £ 

u  o8 'd  a 

©  CO   o  3 

+i    .rH  *C 

.2 
>d 
o 
co 


[136] 


» 50  "2 
S'O  o  9 
^3  2 

ft 

■  sin  c 
9  2  3  ft- 


8J 


o  ? 

13  OS 
«  fc>. 


c-g 


°  2 

■go 

a 


O  w 

ja  a) 
bo 
c  9 


23 


3Q 


!-5  2 


— i  03  <D 


2t« 

+2  o 
id-c  d 

>~3  ft  - 

d  a» 

a?s 

CO 


•2  fee  g  s  ?r 

■§.2S«>,§ 

KSPd-SS 
22  § 


bad 
a43 

5  d  >  2  ?  o 

■3  d  P  PibC+a 
CO 


PI 

™A  O 

2  £  « 

<d  d 
=d 
o 


ftS 


is  If: 

m-.2  o  d  o 

c3  o3  5  gTS 

2  2^3'd 
1.2  P  2 

O  03  fn  M  . 

^  OJ  °  co5  3 

©-£  w  g  o  g 
a>  ft 
S.&S«2  .d 

en  a>     13  T3  o 

oP-2^^5 
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c3  0  7!  2  2  D 

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2^.2  «.2£ 

»^  .<h  d  o  "3 
fe"9  *« 

SO  O  ,2  S  Jj  ?d 

©  oj  13  ^  +a  o3 


•5*>-h  in 

"E  *  2,2  ft 

'      ^  o 


*  2  ft  d 


Average 
Price. 


eg 


Melting 
Point,  F. 


Boiling 
Point,  F. 


Specific 
Weight. 


•o 
S5W 


q 

1—  « 


Molecular 
Weight. 


5H 

o 


O 

M 

w 
+ 

q 

oi 

CI  03 

:  « 

•  o 

:  a 

•  d 

^3  03 


0  I 


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[1371 


INDEX. 


Abney's,  Captain,  papyrography,  112 
preparation  of  paper  with  gela- 
tine, 34 

Actinism,  4 
Agate-ware  trays,  10 
Air-bubbles,  how  to  prevent,  9 
Air-cushion  for  printing  frames,  20 
Albumen  paper,  7,  29,  30 
Ammonium  chloride,  29 
Ammonia,  fuming  with,  32,  34 
Aniline  process,  V  .J.  M.  Gottlieb's,  105 

W.  Willis's,  103 
Anthony's  gelatino-bromide  rapid  print- 
ing paper,  43 
Anthracotypy,  Dr.  A.  Sobacchi's,  115 
Arrow-root  paper,  7,  29,  30 

preparation  of,  33 

fuming,  34 

Bertsch's  sensitizing  machine,  13 
Blue  prints,  6,  55 

corrections  on,  75 

direct  positive,  64 

toning,  62 

with  development,  60 

red  prussiate  prints,  61 
Bristol  board,  Reynold's,  25 
Bromargyrite,  28 
Bromide  of  silver,  28 

emulsion  process,  43 

paper,  44 
Brown  prints,  62 

Brush  for  sensitizing  large  sheets,  15 

Calotype  process,  Fox  Talbot's,  40 

Carbon  prints,  6 

Poitevin's,  with  salts  of  iron,  77 
Haugk  &  Liesegang's,  110 
the  author's,  111 

Cause  of  failure  (in  anthracotypy),  120 

Chadwick's,  Sager,  U.  S.  patent,  63 

Chemicals,  list  of,  126 

Chili,  28 

Chloride  of  silver,  27,  29 

paper,  ordinary,  33,  35 
paper,  permanent  sensitive,  29, 
30,  31,  32 


Chromium  prints,  6 

Mungo  Ponton's,  92 

Cros  &  Vergerand's,  102 

Guardabasiti's,  92 

Halleur's,  101 

Thomas  Fox's,  102 

R.  B.  West's,  93 
Chrysotype  process,  53 
Citro-chloride  of  silver  paper,  30,  31,  32 
Classification  of  heliographic  processes, 6 
Cleaves's  printing  frame,  22 
Cloth  pins,  9 

Coating  paper  with  gelatine,  116 
Coating  paper  with  gelatine  emulsion,  49 
Colas's  ink  pictures,  75  . 
Collache's  direct  positive  blue  print 

process,  73 
Colors,  primary,  3 

complementary,  3 
Combination  pan  for  sensitizing,  etc.,  10 
Converting  blue  prints  into  brown,  62 

into  dark- violet  prints,  62 
Copying  frames,  16 

Prof.  Cleaves's,  22 
Corrections  on  blue  prints,  75 
Cros  &  Vergerand's  chromate  of  silver 

prints,  102 
Cyanotype  or  blue  print  process,  Her- 

schels,  51 
Cyanotype  process,  negative,  56 

direct  positive,  64 
Pellet's,  65 

Pizzighelli  &  Huebl's,  69 

Dark-room  lamp,  44 

Dark-violet  prints,  62 

Davy,  Sir  Humphrey,  35 

Decomposition  of  light,  3 

Device  for  sensitizing  large  sheets,  11, 12 

Developing  and  fixing  bromide  of  silver 

prints,  45 
Development  of  anthracotypes,  119 
Dishes  or  trays,  10 

Drawing,  how  to  place  the  original  in 

the  printing  frame,  24 
Dry  plates,  43 
Dusting-in  processes,  113 


139 


140 


INDEX. 


Earthenware  dishes,  10 
Eastman's  web  printing  press,  1 

permanent  bromide  paper,  43, 46 
Eder,  Dr.  51,  52 
Embolite,  28 

Emulsion  process,  bromide  of  silver,  43 
coating  paper  with  the,  49 
preparation  of  the  gelatine,  47 
Enameled  iron  dishes,  10 
Exposure  to  the  action  of  light,  25 
(in  anthracotypy)  119 

Fabricius,  27 
Faraday, 2 

Ferric  salts,  sensibility  of,  51 

Ferricyanide  of  potassium,  action  of, 
upon  a  film  of  gum  arabic  containing 
a  ferrous  salt,  72 

Fisch's  ink  pictures,  77 

Fixing  silver  prints,  35,  36 

Fixing,  developing  and,  bromide  of  sil- 
ver emulsion  prints,  45 

Fotantracographia,  115 

Foxtype,  102 

Frames,  printing  or  copying,  16 

the  author's,  17 

Prof.  Cleaves's,  22 

H.  Sack's,  20 
Fuming  arrow-root  paper,  34 

with  ammonia,  32 

Gelatine  bromide  of  silver  emulsion,  47 
bromide  paper,  44 
coating  paper  with,  116 
solution  for  platinotypes,  81 
solution  required  in  anthraco- 
typy, H7 

Glass  affected  by  light,  2 

Glass  dishes,  10 

Glass  plate  for  a  printing  frame,  17 
Gottlieb's  U.  S.  patent  direct  chromate 

aniline  process,  105 
Greenish  tone,  giving  the  blue  prints  a,  63 
Guardabasiti's  chromium  process,  92 

Halleur,  D.  G.  E.  H.,  55 

Halleur's  chromate  of  silver  prints,  101 

Haugk,  29 

Haugk  &  Liesegang's  carbon  prints,  110 
sensitizing  solution  for  blue 
prints,  57 

Heliographic  processes,  classification 
of,  6 

Heliography  or  solar  printing,  1 


Herschel,  Sir  John,  35,  51,  56 
Herschel's  iodide  of  starch  pictures,  54 

processes,  53,  56 
Herschel,  Prof.  Alexander,  51,  56 
Horn  silver,  27 

Huebl  &  Pizzighelli's  platinum  pro- 
cess, 81 

Huebl  &  Pizzighelli's  sensitizing  solu- 
tion for  photometer  paper,  57 
Husnick,  49 

Hyposulphite  of  soda,  35,  36 

Ink  pictures,  6,  53 

author's,  76 

Colas's,  75 

A.  Fisch's,  77 

Poitevin's,  75 
Invisible,  photography  of  the,  5 
Iodide  of  potassium,  28 

of  silver,  28 

of  starch  pictures,  54,  78 
Iron  prints,  6,  51 

with  development,  60 
Iron,  salts  of,  15 

Itterheim  &  Pizzighelli's  positive  cyano- 

type  process,  69 
Itterheim 's  nigrographic  direct  positive 

process,  109 

Japanned  trays,  10 
Joltrain,  Clarisse  Zoe,  65 

Kleffel,  34 

Lampblack,  114 
Lapis  infernalis,  28 
Liesegang,  29,  30,  34 
Liesegang  &  Haugk's  carbon  prints,  110 
sensitizing   solution   for  blue 
prints,  57 

Light,  chemical  and  physical  action  of,  2 

decomposition  of,  3 

exposure  to,  25,  44 

glass  affected  by,  2 

ruby-colored,  44 

solar  or  white,  3 
List  of  chemicals,  126 
Lunar  caustic,  28 

Machine,  sensitizing,  13 

Mandel's,  P.  H.,  patented  process,  113 

Marion,  55 

Methods  for  reproducing  the  original 
tracing  as  a  negative,  123 


INDEX. 


141 


Methods,  various,  of  sensitizing,  8 
Mexico,  27,  28 
Monkhoven,  32,  33 
Moonlight,  5 

Negative  cyanotype  process,  56 
Negative,  two  methods  of  producing  the 

original  tracing  as  a,  123 
Newton,  3 

Niepce's  redprussiateof  potash  prints,  61 

Nigrographic  prints,  6 

Nigrographic  direct  positive  process,  It- 

terheim's,  109 
Nitrate  of  silver,  38 

solution,  amount  required,  30 

Original,  how  to  place  in  the  printing 
frame,  24 

Original,  stretching  upon  the  glass,  23 
Original  tracing,  two  mothods  of  pro- 
ducing, as  a  negative,  123 
Ost,  A.,  30 
Oxalate  of  iron,  51 

Pans  for  sensitizing,  etc.,  10 
Paper,  albumen,  7 

arrow-root,  7 

calotype,  41 

citro-chloride  of  silver,  30, 31, 32 
coating,  with  gelatine,  116 
coating,  with  gelat.  emulsion,  49 
dishes,  11 

Eastman's  permanent  bromide 

of  silver,  43^6 
for  heliographic  prints,  7 
ordinary  chloride  of  silver,  33 
permanent  sensitive  chloride  of 

silver,  29 
preparation    of,    with  arrow- 
root, 33 

preservation  of  ordinary  chlo- 
ride of  silver,  35 
Rives's  and  Steinbach's,  116 
sensitive,  prepared  with  citric 

acid,  30,  31,  32 
washed  silver,  32 
Pasteboard  trays,  11 
Papyrography,  Captain  Abney's,  112 
Patent,  Chadwick's  U.S.,  No.  259,094,  63 
Gottlieb's  U.S.,  No.  306,481,  105 
Mandel's  U.  S.,  No.  294,485,  113 
Pellet's  U.  S.,  No.  241,713,  65 
Poitevin'sEng.  No.  2,815, 106, 112 
Sherman's  U.S.,  No.  332,364, 108 


Talbot's  Eng.,  No.  8,842,  40 
Talbot's  Eng.,  No.  9,753,  41 
West's  U.S.,  No.  273,206,  93 
West's  U.S.,  No.  341,083,  96 
West's  U.S.,  No.  345,753,  97 
West's  U.S.,  No.  345,938,  99 
Willis's  U.S.,  No.  213,484,  79 
Pellet's,  Henry,  positive  cyanotype  pro- 
cess, 65 

Permanent  sensitive  chloride  of  silver 

paper,  29 
Peru,  27 
Pettit,  Jas.,  56 
Phipson's  process,  53 
Photographers,  professional,  29 
Photography  of  the  invisible,  5 
Photometer,  58 

Pizzighelli's,  Capt.  G.,  negative  cyano- 
type process,  56 

Pizzighelli's,  Capt.  G.,  and  A.  Huebl's 
sensitizing  solution  for  photometer 
paper,  57 

Pizzighelli's  description  of  anthraco- 
typy, 115 

Pizzighelli's,  Capt.  G.,  and  A.  Huebl's 
recipes  and  remarks  relating  to 
platinotypy,  81 
Pizzighelli's,  Capt.  G.,  and  L.  v.  Itter- 
heim's  modification  of  Herschel's 
cyanotype  process,  69 
Pizzighelli's,  Capt.  G.,  new  platinotype 

process,  without  development,  86 
Platinum  process,  79 

Pizzighelli's  and  Huebl's  reci- 
pes for,  81 
Capt.  Pizzighelli's  new,  with- 
out development,  86 
Wm.  Willis,  jr.'s,  patented,  79 
Poitevin,  Alphonse  Louis,  52,  53 

direct  positive  carbon  prints,  77 
English  patent  No.  2,815, 106,112 
ink  pictures,  75 

pigment  prints  (with  chromium 

salt),  106 
process  with  printing  ink  (direct 
positive),  78 
Ponton's,  Mungo,  chromium  prints,  92 
Porcelain  dishes,  10 
Potassium  ferricyanide,  52 
ferrocyanide,  52 
iodide,  28 
Potash  prints,  red  prussiate  of,  61 
Preservation  of  the  ordinary  chloride  of 
silver  paper,  35 


142 


INDEX. 


Preparation  of  the  gelatine  emulsion,  47 
Printing  frames,  16 

how  to  use,  23 

Hugo  Sack's  pneumatic,  20 

Street's,  with  air  cushion,  20 

the  author's,  17,  19 

glass  plate  for,  17 

without  a  glass  plate,  20 

•  Prof.  Cleaves's,  22 
Prints,  blue,  6,  53,  55,  75 

carbon  or  pigment,  6,  77,  110 

chromium,  6,  91 

in  printing  ink,  78,  112 

in  writing  ink,  6,  53,  75 

iron,  6,  51  to  90 

iodide  of  starch,  54,  78 

nigrographic,  6, 109 

silver,  6,  27  to  50 

silver,  how  long  to  expose,  35 

uranium,  6,  121,  122 
See  also  Process. 
Process,  chrysotype,  53 

bromide  of  silver  emulsion,  43-50 

Colas' s  direct  positive  (ink  pic- 
ture), 75 

Collache's  direct  positive  blue 
print,  73 

Cros  &  Vergerand's  chromate  of 
silver,  102 

dusting-in,  113 

Fisch's  direct  positive  (ink  pic- 
tures), 77 
Gottlieb's  patented  aniline,  105 
Guardabasiti's  chromium,  92 
Halleur's  chromate  of  silver,  101 
Itterheim's  nigrographic,  109 
Jol train's  direct  positive  blue 

print,  73 
Mandel's  patent  dusting-in,  113 
negative  cyanotype,  56 
Pizzighelli's  platinum,  without 

development,  86 
Ponton's  chromium,  92 
Sobacchi's  anthracotypy,  115 
Talbot's  calotype,  40 
Tilhet's  patented  chromium,  106 
Willis's  aniline,  103 
platinum,  79 
See  also  Prints. 
Properties  of  ferric  and  ferrous  salts,  51 
Prussiate  of  potash,  yellow  and  red,  52 
prints,  61 

Quinine,  5 


Rays,  actinic,  4 

of  heat,  4 
of  light,  4 

Recipes  for  blue  prints,  without  devel- 
opment, 56 
Red  prussiate  of  potash,  52 

prints,  61 
Reynold's  bristol  board,  25 

process  with  ferric  oxalate  of 
ammonium,  54 
Rives's  photographic  papers,  116 
Ruby-colored  light,  44 

Sobacchi's,  D.  Alex.,  anthracotypy,  115 
Sack's,    Hugo,    pneumatic  printing 

frame,  20 
Sal  ammoniac,  29 
Salt,  common,  29 
Salts  of  iron,  51 

processes  with,  51 
Salts  of  silver,  27 
Saxony,  27 
Scheele,  27 

Sensibility  of  ferric  salts,  51 

Sensitive  paper,  permanent  citro-chlo- 

ride  of  silver,  29 
Sensitive  paper,  washed,  32 
Sensitizing  by  floating,  8 

by  immersing,  8,  9 

by  means  of  a  sponge  or  brush,  8 

machine,  13,  14 

solutions  for  blue  prints,  56  to  58 
trays  or  dishes,  10  to  13 
various  methods  of,  8 

Sepia  colored  prints,  61 

Sherman's  U.S.  patent  on  indirect  chro- 
mium pigment  prints,  108 

Siberia,  27 

Silver,  bromide  of,  emulsion  process,  43 
chloride,  27,  29 
iodide,  28 

negative  and  blue  print  posi- 
tive, 63 
nitrate,  28,  29 

paper,  ordinary  chloride  of,  33 
prints,  6,  25  to  39 
fixing,  35 

how  long  to  expose,  35 
Talbot's  calotypes,  40 
toning,  37 
washing  fixed,  36 
with  development,  39 

salts,  27 
Soda,  hyposulphite  of,  35 


INDEX. 


143 


Sodium  chloride,  29 

Solar  or  white  light,  3 

Solar  spectrum,  3 

Spectrum,  colors  of  the,  4 

Spring  cloth-pins,  9 

Steinbach's  photographic  papers,  116 

Street's  printing  frame,  20 

Sunlight  printing  process,  1 


Talbot,  Fox,  35,  91 

calotype  process,  40 
Talbot,  Romain,  27 

developing  and  fixing  bromide 
of  silver  prints,  45 
Tartrate  of  iron,  51 
Temporary  paper  dishes,  11 
Tilhet's,  M.,  U.  S.  patent  on  indirect 

chromium  pigment  prints,  106 
Time  of  exposure,  25 
Toning  bath  for  prints  on  washed  silver 

paper,  38 
Toning  blue  prints,  62 
Toning  and  fixing  bath,  Liesegang's 

combined,  39 
Toning  bath  for  prints  on  citro-chloride 

of  silver  paper,  37 


Tracing,  how  to  place  in  the  printing 

frame,  24 
two  methods  of  producing  the 

original  as  a  negative,  123 
Trays  for  sensitizing,  etc.,  10 

Uranium  prints,  6 

salts,  processes  with,  121 

Violet  prints,  62 

Vogel,  Prof.,  2,  23,  27,  29,  34 

iron  prints, with  developmental 
improvements  in  aniline  print- 
ing, 103 
photometer,  58 

Washing  fixed  silver  prints,  36 
Wedgwood,  35 

West's,  R.  B.,  patents  on  photographic 
printing  (with  chromium  salts),  93 
Willet's  Point,  56 
Willis,  Wm,  31 

aniline  process,  103 

platinum  process,  79 
Wooden  Trays,  11 

Yellow  prussiate  of  potash,  52 
Zoellner's  iodide  of  starch  prints,  78 


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